diff --git a/rust/noosphere-core/src/context/content/write.rs b/rust/noosphere-core/src/context/content/write.rs
index e13bf387b..b35e6387c 100644
--- a/rust/noosphere-core/src/context/content/write.rs
+++ b/rust/noosphere-core/src/context/content/write.rs
@@ -158,7 +158,18 @@ where
         let body_cid =
             BodyChunkIpld::store_bytes(&bytes, self.sphere_context_mut().await?.db_mut()).await?;
 
-        self.link(slug, content_type, &body_cid, additional_headers)
+        let header = (
+            Header::ContentLength.to_string(),
+            format!("{}", bytes.len()),
+        );
+        let additional_headers = if let Some(mut headers) = additional_headers {
+            headers.push(header);
+            headers
+        } else {
+            vec![header]
+        };
+
+        self.link(slug, content_type, &body_cid, Some(additional_headers))
             .await
     }
 
diff --git a/rust/noosphere-core/src/context/context.rs b/rust/noosphere-core/src/context/context.rs
index c8f62e1f6..98c25d4ec 100644
--- a/rust/noosphere-core/src/context/context.rs
+++ b/rust/noosphere-core/src/context/context.rs
@@ -256,22 +256,82 @@ mod tests {
     use crate::{
         authority::{generate_capability, generate_ed25519_key, Access, SphereAbility},
         context::{
-            HasMutableSphereContext, HasSphereContext, SphereContentWrite, SpherePetnameWrite,
+            AsyncFileBody, HasMutableSphereContext, HasSphereContext, SphereContentWrite,
+            SpherePetnameWrite,
         },
-        data::{ContentType, LinkRecord, LINK_RECORD_FACT_NAME},
+        data::{ContentType, Header, LinkRecord, LINK_RECORD_FACT_NAME},
         helpers::{make_valid_link_record, simulated_sphere_context},
         tracing::initialize_tracing,
         view::Sphere,
     };
 
-    use noosphere_storage::{MemoryStorage, SphereDb};
+    use noosphere_storage::{MemoryStorage, SphereDb, Storage};
+    use serde_json::json;
     use ucan::{builder::UcanBuilder, crypto::KeyMaterial, store::UcanJwtStore};
+
     #[cfg(target_arch = "wasm32")]
     use wasm_bindgen_test::wasm_bindgen_test;
 
     #[cfg(target_arch = "wasm32")]
     wasm_bindgen_test::wasm_bindgen_test_configure!(run_in_browser);
 
+    #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
+    #[cfg_attr(not(target_arch = "wasm32"), tokio::test)]
+    async fn it_sets_content_length_and_type_on_write() -> Result<()> {
+        initialize_tracing(None);
+
+        let (mut sphere_context, _) = simulated_sphere_context(Access::ReadWrite, None).await?;
+
+        check_headers(
+            &mut sphere_context,
+            "note",
+            ContentType::Text,
+            "hello".as_ref(),
+            "5",
+        )
+        .await?;
+
+        check_headers(
+            &mut sphere_context,
+            "note",
+            ContentType::Json,
+            json!({"foo":true}).to_string().as_ref(),
+            "12",
+        )
+        .await?;
+
+        async fn check_headers<C, S, F>(
+            sphere_context: &mut C,
+            slug: &str,
+            content_type: ContentType,
+            content: F,
+            expected_length: &str,
+        ) -> Result<()>
+        where
+            C: HasMutableSphereContext<S>,
+            S: Storage + 'static,
+            F: AsyncFileBody,
+        {
+            let db = sphere_context.sphere_context().await?.db().clone();
+            let link = sphere_context
+                .write(slug, &content_type, content, None)
+                .await?;
+            let memo = link.load_from(&db).await?;
+            assert_eq!(
+                memo.headers,
+                vec![
+                    (
+                        Header::ContentLength.to_string(),
+                        expected_length.to_owned()
+                    ),
+                    (Header::ContentType.to_string(), content_type.to_string())
+                ]
+            );
+            Ok(())
+        }
+        Ok(())
+    }
+
     #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
     #[cfg_attr(not(target_arch = "wasm32"), tokio::test)]
     async fn it_validates_slug_names_when_writing() -> Result<()> {
diff --git a/rust/noosphere-core/src/data/headers/header.rs b/rust/noosphere-core/src/data/headers/header.rs
index aa00f1121..8965d3d17 100644
--- a/rust/noosphere-core/src/data/headers/header.rs
+++ b/rust/noosphere-core/src/data/headers/header.rs
@@ -2,6 +2,8 @@ use std::{convert::Infallible, fmt::Display, ops::Deref, str::FromStr};
 
 /// Well-known headers in the Noosphere
 pub enum Header {
+    /// The content length (in bytes) of associated binary data
+    ContentLength,
     /// Content-type, for mimes
     ContentType,
     /// A proof, typically a UCAN JWT
@@ -34,6 +36,7 @@ impl FromStr for Header {
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         Ok(match s.to_lowercase().as_str() {
+            "content-length" => Header::ContentLength,
             "content-type" => Header::ContentType,
             "file-extension" => Header::FileExtension,
             "proof" => Header::Proof,
@@ -52,6 +55,7 @@ impl Deref for Header {
 
     fn deref(&self) -> &Self::Target {
         match self {
+            Header::ContentLength => "Content-Length",
             Header::ContentType => "Content-Type",
             Header::Proof => "Proof",
             Header::Author => "Author",
diff --git a/swift/Tests/SwiftNoosphereTests/NoosphereTests.swift b/swift/Tests/SwiftNoosphereTests/NoosphereTests.swift
index c9d001d58..53a63a103 100644
--- a/swift/Tests/SwiftNoosphereTests/NoosphereTests.swift
+++ b/swift/Tests/SwiftNoosphereTests/NoosphereTests.swift
@@ -188,11 +188,12 @@ final class NoosphereTests: XCTestCase {
         var pointer = file_header_names.ptr!;
         
         // NOTE: "hello" is only given once even though there are two headers with that name
-        assert(name_count == 3)
+        assert(name_count == 4)
         
         let expected_headers = [
             ["foo", "bar"],
             ["hello", "world"],
+            ["Content-Length", String(file_bytes.count)],
             ["Content-Type", "text/subtext"]
         ]