From 922988e05212991b476a845c9fb543be80080226 Mon Sep 17 00:00:00 2001
From: vibhor-aggr <vibhor-aggr@users.noreply.github.com>
Date: Thu, 11 Jun 2026 19:23:23 +0530
Subject: [PATCH 1/3] Skip compression for partial content responses

---
 index.js            |  6 ++++++
 test/compression.js | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/index.js b/index.js
index c0638e08..05d66328 100644
--- a/index.js
+++ b/index.js
@@ -171,6 +171,12 @@ function compression (options) {
         return
       }
 
+      // response is partial content
+      if (res.statusCode === 206) {
+        nocompress('partial content')
+        return
+      }
+
       // vary
       vary(res, 'Accept-Encoding')
 
diff --git a/test/compression.js b/test/compression.js
index 8107def0..77de019d 100644
--- a/test/compression.js
+++ b/test/compression.js
@@ -67,6 +67,25 @@ describe('compression()', function () {
       .expect(200, 'hello, world', done)
   })
 
+  it('should skip partial content responses', function (done) {
+    var server = createServer({ threshold: 0 }, function (req, res) {
+      res.statusCode = 206
+      res.setHeader('Content-Type', 'text/plain')
+      res.setHeader('Content-Range', 'bytes 0-4/12')
+      res.setHeader('Content-Length', '5')
+      res.end('hello')
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .set('Range', 'bytes=0-4')
+      .expect(shouldNotHaveHeader('Content-Encoding'))
+      .expect('Content-Range', 'bytes 0-4/12')
+      .expect('Content-Length', '5')
+      .expect(206, 'hello', done)
+  })
+
   it('should set Vary', function (done) {
     var server = createServer({ threshold: 0 }, function (req, res) {
       res.setHeader('Content-Type', 'text/plain')

From 203861ecac431f328a193b947dabc1816610d7ae Mon Sep 17 00:00:00 2001
From: Ulises Gascon <ulisesgascongonzalez@gmail.com>
Date: Wed, 9 Sep 2026 11:45:28 +0200
Subject: [PATCH 2/3] test: cover 206 partial content skip

---
 test/compression.js | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/test/compression.js b/test/compression.js
index 77de019d..6a39df99 100644
--- a/test/compression.js
+++ b/test/compression.js
@@ -79,13 +79,31 @@ describe('compression()', function () {
     request(server)
       .get('/')
       .set('Accept-Encoding', 'gzip')
-      .set('Range', 'bytes=0-4')
       .expect(shouldNotHaveHeader('Content-Encoding'))
+      .expect(shouldNotHaveHeader('Vary'))
       .expect('Content-Range', 'bytes 0-4/12')
       .expect('Content-Length', '5')
       .expect(206, 'hello', done)
   })
 
+  it('should skip partial content responses set via writeHead', function (done) {
+    var server = createServer({ threshold: 0 }, function (req, res) {
+      res.writeHead(206, {
+        'Content-Type': 'text/plain',
+        'Content-Range': 'bytes 0-4/12',
+        'Content-Length': '5'
+      })
+      res.end('hello')
+    })
+
+    request(server)
+      .get('/')
+      .set('Accept-Encoding', 'gzip')
+      .expect(shouldNotHaveHeader('Content-Encoding'))
+      .expect('Content-Range', 'bytes 0-4/12')
+      .expect(206, 'hello', done)
+  })
+
   it('should set Vary', function (done) {
     var server = createServer({ threshold: 0 }, function (req, res) {
       res.setHeader('Content-Type', 'text/plain')

From 63d9224ff7d7b052148344eee150b2d85f3cccb1 Mon Sep 17 00:00:00 2001
From: Ulises Gascon <ulisesgascongonzalez@gmail.com>
Date: Wed, 9 Sep 2026 11:45:33 +0200
Subject: [PATCH 3/3] docs: note 206 partial content skip

---
 HISTORY.md | 5 +++++
 README.md  | 4 +++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/HISTORY.md b/HISTORY.md
index 0678bf2a..5b90a7bc 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,3 +1,8 @@
+unreleased
+==========
+
+  * Skip compression for `206 Partial Content` responses
+
 1.8.1 / 2025-07-17
 ==========
 
diff --git a/README.md b/README.md
index 98c5f38c..39610a29 100644
--- a/README.md
+++ b/README.md
@@ -41,7 +41,9 @@ the middleware, based on the given `options`.
 
 This middleware will never compress responses that include a `Cache-Control`
 header with the [`no-transform` directive](https://tools.ietf.org/html/rfc7234#section-5.2.2.4),
-as compressing will transform the body.
+as compressing will transform the body. It will also never compress
+[`206 Partial Content`](https://www.rfc-editor.org/rfc/rfc9110#section-15.3.7)
+responses, as the `Content-Range` header describes the uncompressed body.
 
 #### Options