HTTP Headers Diff

About this tool

HTTP Headers Diff compares two pasted header blocks and reports what changed from the first set to the second: added headers, removed headers, changed values, and unchanged names. It is useful for release checks, CDN/proxy debugging, security-header reviews, cache-policy changes, and comparing request or response captures.

Header names are matched case-insensitively, repeated headers are combined according to HTTP header-list rules, and Set-Cookie is kept as separate lines instead of being comma-joined. Optional request/status lines such as GET / HTTP/1.1 or HTTP/1.1 200 OK are skipped so you can paste raw captures.

Worked example

First headers:

Content-Type: text/html
Server: nginx
X-Frame-Options: DENY

Second headers:

Content-Type: application/json
Server: nginx
Cache-Control: no-cache

Output:

Header diff — 1 added, 1 removed, 1 changed, 1 unchanged

Added (1):
  + Cache-Control: no-cache

Removed (1):
  - X-Frame-Options: DENY

Changed (1):
  ~ Content-Type: text/html -> application/json

Unchanged (1):
  Server

Use Ignore headers for noisy values such as Date, Age, or request IDs. Turn on Ignore token order when comparing comma-list headers like Cache-Control or Vary where only the ordering changed.

Limits & edge cases

• This is a paste-and-compare tool; it does not fetch live URLs or execute curl commands.
• The diff direction is first/left/old → second/right/new.
• Header names are case-insensitive, but values are compared exactly unless Ignore token order is enabled.
• Repeated headers are joined with , except Set-Cookie, which stays newline-separated.
• Obsolete folded continuation lines are accepted and folded into the previous header value.
• The parser stops at the first blank line, treating anything after it as a message body and ignoring it.

FAQ