[HTTP] Fetch: content-length header is being added to the safe-list

[chrisdavidmills]

Acceptance criteria

1. • The listed features are documented sufficiently on MDN
2. • BCD is updated
3. • Interactive example and data repos are updated if appropriate
4. • The content has been reviewed as needed

Features to document

1. content-length header is being added to the safe-list

Related Gecko bugs

1. • Fetch: content-length header is being added to the safe-list. Needs a rel note, also investigate which pages need updating.

For folks helping with Firefox-related documentation features — make sure above AC have been done, but also:

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes if feature is enabled in release
• Add entry to Firefox experimental features page if feature is not yet enabled in release

[hamishwillee]

1. • BCD is updated
     • Need to add info about versions that this was added to safelisted. [Currently trying to confirm best approach]
2. • Interactive example and data repos are updated if appropriate - NA
3. • Release note - done in Content-Length added to CORs safelisted headers #2766
4. Docs:
   • HTTP headers > Content-Length
     • Need to add that it is safelisted to table up the top
   • Glossary > CORS-safelisted response header - Content-Length already in list, and fact that this was not always in list already noted. No action on this one except maybe a flaw check.
   • HTTP headers > Access-Control-Expose-Headers
     • Already mentions the safe list. Wording can be improved with minor subedit and better cross linking.

All the work done in #2766

[hamishwillee]

Reopening, as still discussing BCD and mdn/browser-compat-data#9456

While above is only open item, I will also address this note based on what happens with BCD: #2766 (comment)

[chrisdavidmills]

So looks like this one is still ongoing., @hamishwillee, although there was movement on the BCD today. Hopefully next day or so...

[hamishwillee]

@chrisdavidmills Well you can close this "if you like". The ongoing work is in improving the BCD. It is related but not strictly necessary to the other docs work.

[chrisdavidmills]

@hamishwillee yeah, let's do that.