diff --git a/spacy/ml/models/__init__.py b/spacy/ml/models/__init__.py
index f032370193f..9b3a5c8bc80 100644
--- a/spacy/ml/models/__init__.py
+++ b/spacy/ml/models/__init__.py
@@ -1,3 +1,4 @@
+from .coref import *
 from .entity_linker import *  # noqa
 from .multi_task import *  # noqa
 from .parser import *  # noqa
diff --git a/spacy/ml/models/coref.py b/spacy/ml/models/coref.py
new file mode 100644
index 00000000000..68ce51bbb7a
--- /dev/null
+++ b/spacy/ml/models/coref.py
@@ -0,0 +1,18 @@
+from typing import List
+from thinc.api import Model
+from thinc.types import Floats2d
+
+from ...util import registry
+from ...tokens import Doc
+
+
+@registry.architectures("spacy.Coref.v0")
+def build_coref_model(
+    tok2vec: Model[List[Doc], List[Floats2d]]
+) -> Model:
+    """Build a coref resolution model, using a provided token-to-vector component.
+    TODO.
+
+    tok2vec (Model[List[Doc], List[Floats2d]]): The token-to-vector subnetwork.
+    """
+    return tok2vec
diff --git a/spacy/pipeline/__init__.py b/spacy/pipeline/__init__.py
index 1fa53a55671..0eecff08f3e 100644
--- a/spacy/pipeline/__init__.py
+++ b/spacy/pipeline/__init__.py
@@ -1,4 +1,6 @@
 from .attributeruler import AttributeRuler
+from .coref import CoreferenceResolver
+from .coref_er import CorefEntityRecognizer
 from .dep_parser import DependencyParser
 from .entity_linker import EntityLinker
 from .ner import EntityRecognizer
diff --git a/spacy/pipeline/coref.py b/spacy/pipeline/coref.py
new file mode 100644
index 00000000000..9ccc2c89f0a
--- /dev/null
+++ b/spacy/pipeline/coref.py
@@ -0,0 +1,288 @@
+from typing import Iterable, Tuple, Optional, Dict, Callable, Any
+
+from thinc.api import get_array_module, Model, Optimizer, set_dropout_rate, Config
+from itertools import islice
+
+from .trainable_pipe import TrainablePipe
+from .coref_er import DEFAULT_MENTIONS
+from ..language import Language
+from ..training import Example, validate_examples, validate_get_examples
+from ..errors import Errors
+from ..scorer import Scorer
+from ..tokens import Doc
+from ..vocab import Vocab
+
+
+default_config = """
+[model]
+@architectures = "spacy.Coref.v0"
+
+[model.tok2vec]
+@architectures = "spacy.Tok2Vec.v2"
+
+[model.tok2vec.embed]
+@architectures = "spacy.MultiHashEmbed.v1"
+width = 64
+rows = [2000, 2000, 1000, 1000, 1000, 1000]
+attrs = ["ORTH", "LOWER", "PREFIX", "SUFFIX", "SHAPE", "ID"]
+include_static_vectors = false
+
+[model.tok2vec.encode]
+@architectures = "spacy.MaxoutWindowEncoder.v2"
+width = ${model.tok2vec.embed.width}
+window_size = 1
+maxout_pieces = 3
+depth = 2
+"""
+DEFAULT_MODEL = Config().from_str(default_config)["model"]
+
+DEFAULT_CLUSTERS_PREFIX = "coref_clusters"
+
+
+@Language.factory(
+    "coref",
+    assigns=[f"doc.spans"],
+    requires=["doc.spans"],
+    default_config={
+        "model": DEFAULT_MODEL,
+        "span_mentions": DEFAULT_MENTIONS,
+        "span_cluster_prefix": DEFAULT_CLUSTERS_PREFIX,
+    },
+    default_score_weights={"coref_f": 1.0, "coref_p": None, "coref_r": None},
+)
+def make_coref(
+    nlp: Language,
+    name: str,
+    model,
+    span_mentions: str,
+    span_cluster_prefix: str,
+) -> "CoreferenceResolver":
+    """Create a CoreferenceResolver component. TODO
+
+    model (Model[List[Doc], List[Floats2d]]): A model instance that predicts ...
+    threshold (float): Cutoff to consider a prediction "positive".
+    """
+    return CoreferenceResolver(
+        nlp.vocab,
+        model,
+        name,
+        span_mentions=span_mentions,
+        span_cluster_prefix=span_cluster_prefix,
+    )
+
+
+class CoreferenceResolver(TrainablePipe):
+    """Pipeline component for coreference resolution.
+
+    DOCS: https://spacy.io/api/coref (TODO)
+    """
+
+    def __init__(
+        self,
+        vocab: Vocab,
+        model: Model,
+        name: str = "coref",
+        *,
+        span_mentions: str,
+        span_cluster_prefix: str,
+    ) -> None:
+        """Initialize a coreference resolution component.
+
+        vocab (Vocab): The shared vocabulary.
+        model (thinc.api.Model): The Thinc Model powering the pipeline component.
+        name (str): The component instance name, used to add entries to the
+            losses during training.
+        span_mentions (str): Key in doc.spans where the candidate coref mentions
+            are stored in.
+        span_cluster_prefix (str): Prefix for the key in doc.spans to store the
+            coref clusters in.
+
+        DOCS: https://spacy.io/api/coref#init (TODO)
+        """
+        self.vocab = vocab
+        self.model = model
+        self.name = name
+        self.span_mentions = span_mentions
+        self.span_cluster_prefix = span_cluster_prefix
+        self._rehearsal_model = None
+        self.cfg = {}
+
+    def predict(self, docs: Iterable[Doc]):
+        """Apply the pipeline's model to a batch of docs, without modifying them.
+        TODO: write actual algorithm
+
+        docs (Iterable[Doc]): The documents to predict.
+        RETURNS: The models prediction for each document.
+
+        DOCS: https://spacy.io/api/coref#predict (TODO)
+        """
+        clusters_by_doc = []
+        for i, doc in enumerate(docs):
+            clusters = []
+            for span in doc.spans[self.span_mentions]:
+                clusters.append([span])
+            clusters_by_doc.append(clusters)
+        return clusters_by_doc
+
+    def set_annotations(self, docs: Iterable[Doc], clusters_by_doc) -> None:
+        """Modify a batch of Doc objects, using pre-computed scores.
+
+        docs (Iterable[Doc]): The documents to modify.
+        clusters: The span clusters, produced by CoreferenceResolver.predict.
+
+        DOCS: https://spacy.io/api/coref#set_annotations (TODO)
+        """
+        if len(docs) != len(clusters_by_doc):
+            raise ValueError("Found coref clusters incompatible with the "
+                             "documents provided to the 'coref' component. "
+                             "This is likely a bug in spaCy.")
+        for doc, clusters in zip(docs, clusters_by_doc):
+            index = 0
+            for cluster in clusters:
+                key = self.span_cluster_prefix + str(index)
+                if key in doc.spans:
+                    raise ValueError(f"Couldn't store the results of {self.name}, as the key "
+                                     f"{key} already exists in 'doc.spans'.")
+                doc.spans[key] = cluster
+                index += 1
+
+    def update(
+        self,
+        examples: Iterable[Example],
+        *,
+        drop: float = 0.0,
+        sgd: Optional[Optimizer] = None,
+        losses: Optional[Dict[str, float]] = None,
+    ) -> Dict[str, float]:
+        """Learn from a batch of documents and gold-standard information,
+        updating the pipe's model. Delegates to predict and get_loss.
+
+        examples (Iterable[Example]): A batch of Example objects.
+        drop (float): The dropout rate.
+        sgd (thinc.api.Optimizer): The optimizer.
+        losses (Dict[str, float]): Optional record of the loss during training.
+            Updated using the component name as the key.
+        RETURNS (Dict[str, float]): The updated losses dictionary.
+
+        DOCS: https://spacy.io/api/coref#update (TODO)
+        """
+        if losses is None:
+            losses = {}
+        losses.setdefault(self.name, 0.0)
+        validate_examples(examples, "CoreferenceResolver.update")
+        if not any(len(eg.predicted) if eg.predicted else 0 for eg in examples):
+            # Handle cases where there are no tokens in any docs.
+            return losses
+        set_dropout_rate(self.model, drop)
+        scores, bp_scores = self.model.begin_update([eg.predicted for eg in examples])
+        # TODO below
+        # loss, d_scores = self.get_loss(examples, scores)
+        # bp_scores(d_scores)
+        if sgd is not None:
+            self.finish_update(sgd)
+        # losses[self.name] += loss
+        return losses
+
+    def rehearse(
+        self,
+        examples: Iterable[Example],
+        *,
+        drop: float = 0.0,
+        sgd: Optional[Optimizer] = None,
+        losses: Optional[Dict[str, float]] = None,
+    ) -> Dict[str, float]:
+        """Perform a "rehearsal" update from a batch of data. Rehearsal updates
+        teach the current model to make predictions similar to an initial model,
+        to try to address the "catastrophic forgetting" problem. This feature is
+        experimental.
+
+        examples (Iterable[Example]): A batch of Example objects.
+        drop (float): The dropout rate.
+        sgd (thinc.api.Optimizer): The optimizer.
+        losses (Dict[str, float]): Optional record of the loss during training.
+            Updated using the component name as the key.
+        RETURNS (Dict[str, float]): The updated losses dictionary.
+
+        DOCS: https://spacy.io/api/coref#rehearse (TODO)
+        """
+        if losses is not None:
+            losses.setdefault(self.name, 0.0)
+        if self._rehearsal_model is None:
+            return losses
+        validate_examples(examples, "CoreferenceResolver.rehearse")
+        docs = [eg.predicted for eg in examples]
+        if not any(len(doc) for doc in docs):
+            # Handle cases where there are no tokens in any docs.
+            return losses
+        set_dropout_rate(self.model, drop)
+        scores, bp_scores = self.model.begin_update(docs)
+        # TODO below
+        target = self._rehearsal_model(examples)
+        gradient = scores - target
+        bp_scores(gradient)
+        if sgd is not None:
+            self.finish_update(sgd)
+        if losses is not None:
+            losses[self.name] += (gradient ** 2).sum()
+        return losses
+
+    def add_label(self, label: str) -> int:
+        """Technically this method should be implemented from TrainablePipe,
+        but it is not relevant for the coref component.
+        """
+        raise NotImplementedError(
+            Errors.E931.format(
+                parent="CoreferenceResolver", method="add_label", name=self.name
+            )
+        )
+
+    def get_loss(self, examples: Iterable[Example], scores) -> Tuple[float, float]:
+        """Find the loss and gradient of loss for the batch of documents and
+        their predicted scores.
+
+        examples (Iterable[Examples]): The batch of examples.
+        scores: Scores representing the model's predictions.
+        RETURNS (Tuple[float, float]): The loss and the gradient.
+
+        DOCS: https://spacy.io/api/coref#get_loss (TODO)
+        """
+        validate_examples(examples, "CoreferenceResolver.get_loss")
+        # TODO
+        return None
+
+    def initialize(
+        self,
+        get_examples: Callable[[], Iterable[Example]],
+        *,
+        nlp: Optional[Language] = None,
+    ) -> None:
+        """Initialize the pipe for training, using a representative set
+        of data examples.
+
+        get_examples (Callable[[], Iterable[Example]]): Function that
+            returns a representative sample of gold-standard Example objects.
+        nlp (Language): The current nlp object the component is part of.
+
+        DOCS: https://spacy.io/api/coref#initialize (TODO)
+        """
+        validate_get_examples(get_examples, "CoreferenceResolver.initialize")
+        subbatch = list(islice(get_examples(), 10))
+        doc_sample = [eg.reference for eg in subbatch]
+        assert len(doc_sample) > 0, Errors.E923.format(name=self.name)
+        self.model.initialize(X=doc_sample)
+
+    def score(self, examples: Iterable[Example], **kwargs) -> Dict[str, Any]:
+        """Score a batch of examples.
+
+        examples (Iterable[Example]): The examples to score.
+        RETURNS (Dict[str, Any]): The scores, produced by Scorer.score_coref.
+
+        DOCS: https://spacy.io/api/coref#score (TODO)
+        """
+        def clusters_getter(doc, span_key):
+            return [spans for name, spans in doc.spans.items() if name.startswith(span_key)]
+        validate_examples(examples, "CoreferenceResolver.score")
+        kwargs.setdefault("getter", clusters_getter)
+        kwargs.setdefault("attr", self.span_cluster_prefix)
+        kwargs.setdefault("include_label", False)
+        return Scorer.score_clusters(examples, **kwargs)
diff --git a/spacy/pipeline/coref_er.py b/spacy/pipeline/coref_er.py
new file mode 100644
index 00000000000..585bdafddb4
--- /dev/null
+++ b/spacy/pipeline/coref_er.py
@@ -0,0 +1,227 @@
+from typing import Optional, Union, Iterable, Callable, List, Dict, Any
+from pathlib import Path
+import srsly
+
+from .pipe import Pipe
+from ..scorer import Scorer
+from ..training import Example
+from ..language import Language
+from ..tokens import Doc, Span, SpanGroup
+from ..matcher import Matcher
+from ..util import ensure_path, to_disk, from_disk, SimpleFrozenList
+
+
+DEFAULT_MENTIONS = "coref_mentions"
+DEFAULT_MATCHER_KEY = "POS"
+DEFAULT_MATCHER_VALUES = ["PROPN", "PRON"]
+
+
+@Language.factory(
+    "coref_er",
+    assigns=[f"doc.spans"],
+    requires=["doc.ents", "token.ent_iob", "token.ent_type", "token.pos"],
+    default_config={
+        "span_mentions": DEFAULT_MENTIONS,
+        "matcher_key": DEFAULT_MATCHER_KEY,
+        "matcher_values": DEFAULT_MATCHER_VALUES,
+    },
+    default_score_weights={
+        "coref_mentions_f": None,
+        "coref_mentions_p": None,
+        "coref_mentions_r": 1.0,  # the mentions data needs to be consistently annotated for precision rates to make sense
+    },
+)
+def make_coref_er(nlp: Language, name: str, span_mentions: str, matcher_key: str, matcher_values: List[str]):
+    return CorefEntityRecognizer(
+        nlp, name, span_mentions=span_mentions, matcher_key=matcher_key, matcher_values=matcher_values
+    )
+
+
+class CorefEntityRecognizer(Pipe):
+    """TODO.
+
+        DOCS: https://spacy.io/api/coref_er (TODO)
+        USAGE: https://spacy.io/usage (TODO)
+        """
+
+    def __init__(
+        self,
+        nlp: Language,
+        name: str = "coref_er",
+        *,
+        span_mentions: str,
+        matcher_key: str,
+        matcher_values: List[str],
+    ) -> None:
+        """Initialize the entity recognizer for coreference mentions. TODO
+
+        nlp (Language): The shared nlp object.
+        name (str): Instance name of the current pipeline component. Typically
+            passed in automatically from the factory when the component is
+            added.
+        span_mentions (str): Key in doc.spans to store the coref mentions in.
+        matcher_key (List[str]): Field for the matcher to work on (e.g. "POS" or "TAG")
+        matcher_values (List[str]): Values to match token sequences as
+            plausible coref mentions
+
+        DOCS: https://spacy.io/api/coref_er#init (TODO)
+        """
+        self.nlp = nlp
+        self.name = name
+        self.span_mentions = span_mentions
+        self.matcher_key = matcher_key
+        self.matcher_values = matcher_values
+        self.matcher = Matcher(nlp.vocab)
+        # TODO: allow to specify any matcher patterns instead?
+        for value in matcher_values:
+            self.matcher.add(
+                f"{value}_SEQ", [[{matcher_key: value, "OP": "+"}]], greedy="LONGEST"
+            )
+
+    @staticmethod
+    def _string_offset(span: Span):
+        return f"{span.start}-{span.end}"
+
+    def __call__(self, doc: Doc) -> Doc:
+        """Find relevant coref mentions in the document and add them
+        to the doc's relevant span container.
+
+        doc (Doc): The Doc object in the pipeline.
+        RETURNS (Doc): The Doc with added entities, if available.
+
+        DOCS: https://spacy.io/api/coref_er#call (TODO)
+        """
+        error_handler = self.get_error_handler()
+        try:
+            # Add NER
+            spans = list(doc.ents)
+            offsets = set()
+            offsets.update([self._string_offset(e) for e in doc.ents])
+
+            # pronouns and proper nouns
+            try:
+                matches = self.matcher(doc, as_spans=True)
+            except ValueError:
+                raise ValueError(f"Could not run the matcher for 'coref_er'. If {self.matcher_key} tags "
+                                 "are not available, change the 'matcher_key' in the config, "
+                                 "or set matcher_values to an empty list.")
+            spans.extend([m for m in matches if self._string_offset(m) not in offsets])
+            offsets.update([self._string_offset(m) for m in matches])
+
+            # noun_chunks - only if implemented and parsing information is available
+            try:
+                spans.extend(
+                    [nc for nc in doc.noun_chunks if self._string_offset(nc) not in offsets]
+                )
+                offsets.update([self._string_offset(nc) for nc in doc.noun_chunks])
+            except (NotImplementedError, ValueError):
+                pass
+
+            self.set_annotations(doc, spans)
+            return doc
+        except Exception as e:
+            error_handler(self.name, self, [doc], e)
+
+    def set_annotations(self, doc, spans):
+        """Modify the document in place"""
+        group = SpanGroup(doc, name=self.span_mentions, spans=spans)
+        if self.span_mentions in doc.spans:
+            raise ValueError(f"Couldn't store the results of {self.name}, as the key "
+                             f"{self.span_mentions} already exists in 'doc.spans'.")
+        doc.spans[self.span_mentions] = group
+
+    def initialize(
+        self,
+        get_examples: Callable[[], Iterable[Example]],
+        *,
+        nlp: Optional[Language] = None,
+    ):
+        """Initialize the pipe for training.
+
+        get_examples (Callable[[], Iterable[Example]]): Function that
+            returns a representative sample of gold-standard Example objects.
+        nlp (Language): The current nlp object the component is part of.
+
+        DOCS: https://spacy.io/api/coref_er#initialize (TODO)
+        """
+        pass
+
+    def from_bytes(
+        self, bytes_data: bytes, *, exclude: Iterable[str] = SimpleFrozenList()
+    ) -> "CorefEntityRecognizer":
+        """Load the coreference entity recognizer from a bytestring.
+
+        bytes_data (bytes): The bytestring to load.
+        RETURNS (CorefEntityRecognizer): The loaded coreference entity recognizer.
+
+        DOCS: https://spacy.io/api/coref_er#from_bytes
+        """
+        cfg = srsly.msgpack_loads(bytes_data)
+        self.span_mentions = cfg.get("span_mentions", DEFAULT_MENTIONS)
+        self.matcher_key = cfg.get("matcher_key", DEFAULT_MATCHER_KEY)
+        self.matcher_values = cfg.get("matcher_values", DEFAULT_MATCHER_VALUES)
+        return self
+
+    def to_bytes(self, *, exclude: Iterable[str] = SimpleFrozenList()) -> bytes:
+        """Serialize the coreference entity recognizer to a bytestring.
+
+        RETURNS (bytes): The serialized component.
+
+        DOCS: https://spacy.io/api/coref_er#to_bytes (TODO)
+        """
+        serial = {"span_mentions": self.span_mentions}
+        return srsly.msgpack_dumps(serial)
+
+    def from_disk(
+        self, path: Union[str, Path], *, exclude: Iterable[str] = SimpleFrozenList()
+    ) -> "CorefEntityRecognizer":
+        """Load the coreference entity recognizer  from a file.
+
+        path (str / Path): The JSONL file to load.
+        RETURNS (CorefEntityRecognizer): The loaded coreference entity recognizer .
+
+        DOCS: https://spacy.io/api/coref_er#from_disk (TODO)
+        """
+        path = ensure_path(path)
+        cfg = {}
+        deserializers_cfg = {"cfg": lambda p: cfg.update(srsly.read_json(p))}
+        from_disk(path, deserializers_cfg, {})
+        self.span_mentions = cfg.get("span_mentions", DEFAULT_MENTIONS)
+        self.matcher_key = cfg.get("matcher_key", DEFAULT_MATCHER_KEY)
+        self.matcher_values = cfg.get("matcher_values", DEFAULT_MATCHER_VALUES)
+        return self
+
+    def to_disk(
+        self, path: Union[str, Path], *, exclude: Iterable[str] = SimpleFrozenList()
+    ) -> None:
+        """Save the coreference entity recognizer to a directory.
+
+        path (str / Path): The JSONL file to save.
+
+        DOCS: https://spacy.io/api/coref_er#to_disk (TODO)
+        """
+        path = ensure_path(path)
+        cfg = {
+            "span_mentions": self.span_mentions,
+            "matcher_key": self.matcher_key,
+            "matcher_values": self.matcher_values,
+        }
+        serializers = {"cfg": lambda p: srsly.write_json(p, cfg)}
+        to_disk(path, serializers, {})
+
+    def score(self, examples: Iterable[Example], **kwargs) -> Dict[str, Any]:
+        """Score a batch of examples.
+
+        examples (Iterable[Example]): The examples to score.
+        RETURNS (Dict[str, Any]): The scores, produced by Scorer.score_coref.
+
+        DOCS: https://spacy.io/api/coref_er#score (TODO)
+        """
+        def mentions_getter(doc, span_key):
+            return doc.spans[span_key]
+        # This will work better once PR 7209 is merged
+        kwargs.setdefault("getter", mentions_getter)
+        kwargs.setdefault("attr", self.span_mentions)
+        kwargs.setdefault("include_label", False)
+        kwargs.setdefault("allow_overlap", True)
+        return Scorer.score_spans(examples, **kwargs)
diff --git a/spacy/pipeline/entityruler.py b/spacy/pipeline/entityruler.py
index 25bc3abeeb9..d6927dddc7b 100644
--- a/spacy/pipeline/entityruler.py
+++ b/spacy/pipeline/entityruler.py
@@ -56,8 +56,7 @@ class EntityRuler(Pipe):
     """The EntityRuler lets you add spans to the `Doc.ents` using token-based
     rules or exact phrase matches. It can be combined with the statistical
     `EntityRecognizer` to boost accuracy, or used on its own to implement a
-    purely rule-based entity recognition system. After initialization, the
-    component is typically added to the pipeline using `nlp.add_pipe`.
+    purely rule-based entity recognition system.
 
     DOCS: https://spacy.io/api/entityruler
     USAGE: https://spacy.io/usage/rule-based-matching#entityruler
diff --git a/spacy/pipeline/textcat.py b/spacy/pipeline/textcat.py
index f94bde84f3e..b8b32f53498 100644
--- a/spacy/pipeline/textcat.py
+++ b/spacy/pipeline/textcat.py
@@ -1,8 +1,8 @@
-from itertools import islice
 from typing import Iterable, Tuple, Optional, Dict, List, Callable, Any
 from thinc.api import get_array_module, Model, Optimizer, set_dropout_rate, Config
 from thinc.types import Floats2d
 import numpy
+from itertools import islice
 
 from .trainable_pipe import TrainablePipe
 from ..language import Language
diff --git a/spacy/scorer.py b/spacy/scorer.py
index f28cb5639c1..969f6529387 100644
--- a/spacy/scorer.py
+++ b/spacy/scorer.py
@@ -341,7 +341,7 @@ def score_spans(
             for label in labels:
                 if label not in score_per_type:
                     score_per_type[label] = PRFScore()
-            # Find all predidate labels, for all and per type
+            # Find all instances, for all and per type
             gold_spans = set()
             pred_spans = set()
             for span in getter(gold_doc, attr):
@@ -373,6 +373,114 @@ def score_spans(
                 f"{attr}_per_type": None,
             }
 
+    @staticmethod
+    def score_clusters(
+        examples: Iterable[Example],
+        attr: str,
+        *,
+        getter: Callable[[Doc, str], Iterable[Iterable[Span]]] = getattr,
+        has_annotation: Optional[Callable[[Doc], bool]] = None,
+        include_label: bool = True,
+        **cfg,
+    ) -> Dict[str, Any]:
+        """Returns PRF scores for clustered spans.
+
+        examples (Iterable[Example]): Examples to score
+        attr (str): The attribute to score.
+        getter (Callable[[Doc, str], Iterable[Iterable[Span]]]): Defaults to getattr.
+            If provided, getter(doc, attr) should return the lists of spans for the
+            individual doc.
+        has_annotation (Optional[Callable[[Doc], bool]]) should return whether a `Doc`
+            has annotation for this `attr`. Docs without annotation are skipped for
+            scoring purposes.
+        include_label (bool): Whether or not to include label information in
+            the evaluation. If set to 'False', two spans will be considered
+            equal if their start and end match, irrespective of their label.
+
+        RETURNS (Dict[str, Any]): A dictionary containing the PRF scores under
+            the keys attr_p/r/f and the per-type PRF scores under attr_per_type.
+
+        DOCS: https://spacy.io/api/scorer#score_clusters (TODO)
+        """
+        # Note: the current implementation just scores binary pairs on whether they
+        # are in the same cluster or not.
+        # TODO: look at different cluster/coreference scoring techniques.
+        score = PRFScore()
+        score_per_type = dict()
+        for example in examples:
+            pred_doc = example.predicted
+            gold_doc = example.reference
+            # Option to handle docs without sents
+            if has_annotation is not None:
+                if not has_annotation(gold_doc):
+                    continue
+            # Find all labels in gold and doc
+            gold_clusters = list(getter(gold_doc, attr))
+            pred_clusters = list(getter(pred_doc, attr))
+            labels = set(
+                [span.label_ for span_list in gold_clusters for span in span_list]
+                + [span.label_ for span_list in pred_clusters for span in span_list]
+            )
+            # Set up all labels for per type scoring and prepare gold per type
+            for label in labels:
+                if label not in score_per_type:
+                    score_per_type[label] = PRFScore()
+            # Find all instances, for all and per type
+            gold_instances = set()
+            gold_per_type = {label: set() for label in labels}
+            for gold_cluster in gold_clusters:
+                for span1 in gold_cluster:
+                    for span2 in gold_cluster:
+                        # only record pairs where span1 comes before span2
+                        if (span1.start < span2.start) or (span1.start == span2.start and span1.end < span2.end):
+                            if include_label:
+                                gold_rel = (span1.label_, span1.start, span1.end - 1, span2.label_, span2.start, span2.end - 1)
+                            else:
+                                gold_rel = (span1.start, span1.end - 1, span2.start, span2.end - 1)
+                            gold_instances.add(gold_rel)
+                            if span1.label_ == span2.label_:
+                                gold_per_type[span1.label_].add(gold_rel)
+            pred_instances = set()
+            pred_per_type = {label: set() for label in labels}
+            for pred_cluster in pred_clusters:
+                for span1 in pred_cluster:
+                    for span2 in pred_cluster:
+                        if (span1.start < span2.start) or (span1.start == span2.start and span1.end < span2.end):
+                            if include_label:
+                                pred_rel = (span1.label_, span1.start, span1.end - 1, span2.label_, span2.start, span2.end - 1)
+                            else:
+                                pred_rel = (span1.start, span1.end - 1, span2.start, span2.end - 1)
+                            pred_instances.add(pred_rel)
+                            if span1.label_ == span2.label_:
+                                pred_per_type[span1.label_].add(pred_rel)
+            # Scores per label
+            if include_label:
+                for k, v in score_per_type.items():
+                    if k in pred_per_type:
+                        v.score_set(pred_per_type[k], gold_per_type[k])
+            # Score for all labels
+            score.score_set(pred_instances, gold_instances)
+        # Assemble final result
+        final_scores = {
+            f"{attr}_p": None,
+            f"{attr}_r": None,
+            f"{attr}_f": None,
+
+        }
+        if include_label:
+            final_scores[f"{attr}_per_type"] = None
+        if len(score) > 0:
+            final_scores[f"{attr}_p"] = score.precision
+            final_scores[f"{attr}_r"] = score.recall
+            final_scores[f"{attr}_f"] = score.fscore
+            return {
+                f"{attr}_p": None,
+                f"{attr}_r": None,
+                f"{attr}_f": None,
+                f"{attr}_per_type": None,
+            }
+        return final_scores
+
     @staticmethod
     def score_cats(
         examples: Iterable[Example],
@@ -722,12 +830,7 @@ def get_ner_prf(examples: Iterable[Example]) -> Dict[str, Any]:
             "ents_per_type": {k: v.to_dict() for k, v in score_per_type.items()},
         }
     else:
-        return {
-            "ents_p": None,
-            "ents_r": None,
-            "ents_f": None,
-            "ents_per_type": None,
-        }
+        return {"ents_p": None, "ents_r": None, "ents_f": None, "ents_per_type": None}
 
 
 # The following implementation of roc_auc_score() is adapted from
diff --git a/spacy/tests/pipeline/test_coref.py b/spacy/tests/pipeline/test_coref.py
new file mode 100644
index 00000000000..ab3de704492
--- /dev/null
+++ b/spacy/tests/pipeline/test_coref.py
@@ -0,0 +1,180 @@
+import pytest
+import spacy
+from spacy.matcher import PhraseMatcher
+from spacy.training import Example
+from spacy.lang.en import English
+from spacy.tests.util import make_tempdir
+from spacy.tokens import Doc
+from spacy.pipeline.coref import DEFAULT_CLUSTERS_PREFIX
+from spacy.pipeline.coref_er import DEFAULT_MENTIONS
+
+
+# fmt: off
+TRAIN_DATA = [
+    (
+        "John Smith told Laura that he was running late and asked her whether she could pick up their kids.",
+        {
+            "spans": {
+                DEFAULT_MENTIONS: [
+                    (0, 10, "MENTION"),
+                    (16, 21, "MENTION"),
+                    (27, 29, "MENTION"),
+                    (57, 60, "MENTION"),
+                    (69, 72, "MENTION"),
+                    (87, 92, "MENTION"),
+                    (87, 97, "MENTION"),
+                ],
+                f"{DEFAULT_CLUSTERS_PREFIX}_1": [
+                    (0, 10, "MENTION"),     # John
+                    (27, 29, "MENTION"),
+                    (87, 92, "MENTION"),    # 'their' refers to John and Laur
+                ],
+                f"{DEFAULT_CLUSTERS_PREFIX}_2": [
+                    (16, 21, "MENTION"),     # Laura
+                    (57, 60, "MENTION"),
+                    (69, 72, "MENTION"),
+                    (87, 92, "MENTION"),     # 'their' refers to John and Laura
+                ],
+            }
+        },
+    ),
+    (
+        "Yes, I noticed that many friends around me received it. It seems that almost everyone received this SMS.",
+        {
+            "spans": {
+                DEFAULT_MENTIONS: [
+                    (5, 6, "MENTION"),
+                    (40, 42, "MENTION"),
+                    (52, 54, "MENTION"),
+                    (95, 103, "MENTION"),
+                ],
+                f"{DEFAULT_CLUSTERS_PREFIX}_1": [
+                    (5, 6, "MENTION"),      # I
+                    (40, 42, "MENTION"),
+
+                ],
+                f"{DEFAULT_CLUSTERS_PREFIX}_2": [
+                    (52, 54, "MENTION"),     # SMS
+                    (95, 103, "MENTION"),
+                ]
+            }
+        },
+    ),
+]
+# fmt: on
+
+
+@pytest.fixture
+def nlp():
+    return English()
+
+
+@pytest.fixture
+def examples(nlp):
+    examples = []
+    for text, annot in TRAIN_DATA:
+        # eg = Example.from_dict(nlp.make_doc(text), annot)
+        # if PR #7197 is merged, replace below with above line
+        ref_doc = nlp.make_doc(text)
+        for key, span_list in annot["spans"].items():
+            spans = []
+            for span_tuple in span_list:
+                start_char = span_tuple[0]
+                end_char = span_tuple[1]
+                label = span_tuple[2]
+                span = ref_doc.char_span(start_char, end_char, label=label)
+                spans.append(span)
+            ref_doc.spans[key] = spans
+        eg = Example(nlp.make_doc(text), ref_doc)
+        examples.append(eg)
+    return examples
+
+
+def test_coref_er_no_POS(nlp):
+    doc = nlp("The police woman talked to him.")
+    coref_er = nlp.add_pipe("coref_er", last=True)
+    with pytest.raises(ValueError):
+        coref_er(doc)
+
+
+def test_coref_er_with_POS(nlp):
+    words = ["The", "police", "woman", "talked", "to", "him", "."]
+    pos = ["DET", "NOUN", "NOUN", "VERB", "ADP", "PRON", "PUNCT"]
+    doc = Doc(nlp.vocab, words=words, pos=pos)
+    coref_er = nlp.add_pipe("coref_er", last=True)
+    coref_er(doc)
+    assert len(doc.spans[coref_er.span_mentions]) == 1
+    mention = doc.spans[coref_er.span_mentions][0]
+    assert (mention.text, mention.start, mention.end) == ("him", 5, 6)
+
+
+def test_coref_er_custom_POS(nlp):
+    words = ["The", "police", "woman", "talked", "to", "him", "."]
+    pos = ["DET", "NOUN", "NOUN", "VERB", "ADP", "PRON", "PUNCT"]
+    doc = Doc(nlp.vocab, words=words, pos=pos)
+    config = {"matcher_key": "POS", "matcher_values": ["NOUN"]}
+    coref_er = nlp.add_pipe("coref_er", last=True, config=config)
+    coref_er(doc)
+    assert len(doc.spans[coref_er.span_mentions]) == 1
+    mention = doc.spans[coref_er.span_mentions][0]
+    assert (mention.text, mention.start, mention.end) == ("police woman", 1, 3)
+
+
+def test_coref_clusters(nlp, examples):
+    coref_er = nlp.add_pipe("coref_er", last=True)
+    coref = nlp.add_pipe("coref", last=True)
+    coref.initialize(lambda: examples)
+    words = ["Laura", "walked", "her", "dog", "."]
+    pos = ["PROPN", "VERB", "PRON", "NOUN", "PUNCT"]
+    doc = Doc(nlp.vocab, words=words, pos=pos)
+    coref_er(doc)
+    coref(doc)
+    assert len(doc.spans[coref_er.span_mentions]) > 0
+    found_clusters = 0
+    for name, spans in doc.spans.items():
+        if name.startswith(coref.span_cluster_prefix):
+            found_clusters += 1
+    assert found_clusters > 0
+
+
+def test_coref_er_score(nlp, examples):
+    config = {"matcher_key": "POS", "matcher_values": []}
+    coref_er = nlp.add_pipe("coref_er", last=True, config=config)
+    coref = nlp.add_pipe("coref", last=True)
+    coref.initialize(lambda: examples)
+    mentions_key = coref_er.span_mentions
+    cluster_prefix_key = coref.span_cluster_prefix
+    matcher = PhraseMatcher(nlp.vocab)
+    terms_1 = ["Laura", "her", "she"]
+    terms_2 = ["it", "this SMS"]
+    matcher.add("A", [nlp.make_doc(text) for text in terms_1])
+    matcher.add("B", [nlp.make_doc(text) for text in terms_2])
+    for eg in examples:
+        pred = eg.predicted
+        matches = matcher(pred, as_spans=True)
+        pred.set_ents(matches)
+        coref_er(pred)
+        coref(pred)
+        eg.predicted = pred
+        # TODO: if #7209 is merged, experiment with 'include_label'
+        scores = coref_er.score([eg])
+        assert f"{mentions_key}_f" in scores
+        scores = coref.score([eg])
+        assert f"{cluster_prefix_key}_f" in scores
+
+
+def test_coref_serialization(nlp):
+    # Test that the coref component can be serialized
+    config_er = {"matcher_key": "TAG", "matcher_values": ["NN"]}
+    nlp.add_pipe("coref_er", last=True, config=config_er)
+    nlp.add_pipe("coref", last=True)
+    assert "coref_er" in nlp.pipe_names
+    assert "coref" in nlp.pipe_names
+
+    with make_tempdir() as tmp_dir:
+        nlp.to_disk(tmp_dir)
+        nlp2 = spacy.load(tmp_dir)
+        assert "coref_er" in nlp2.pipe_names
+        assert "coref" in nlp2.pipe_names
+        coref_er_2 = nlp2.get_pipe("coref_er")
+        assert coref_er_2.matcher_key == "TAG"
diff --git a/spacy/tokens/_dict_proxies.py b/spacy/tokens/_dict_proxies.py
index 9ee1ad02f70..6194cdeffec 100644
--- a/spacy/tokens/_dict_proxies.py
+++ b/spacy/tokens/_dict_proxies.py
@@ -13,7 +13,7 @@
 
 # Why inherit from UserDict instead of dict here?
 # Well, the 'dict' class doesn't necessarily delegate everything nicely,
-# for performance reasons. The UserDict is slower by better behaved.
+# for performance reasons. The UserDict is slower but better behaved.
 # See https://treyhunner.com/2019/04/why-you-shouldnt-inherit-from-list-and-dict-in-python/0ww
 class SpanGroups(UserDict):
     """A dict-like proxy held by the Doc, to control access to span groups."""