Bug 289445 – "Save as" uses the file extension name instead of the URL Content-Type

• Component: Media
• Status: RESOLVED FIXED

[Jeff Johnson]

Created attachment 474504 [details]
Screenshot of opening the downloaded video in Finder

Steps to reproduce:
1) Open https://www.reddit.com/media?url=https%3A%2F%2Fexternal-preview.redd.it%2Fyhb1f6aAABHf5frJUF4mHku3JTgwbg2gl7Wco76dyjA.gif%3Fwidth%3D308%26format%3Dmp4%26s%3D88a3fadf350d2eb9a9c97192a9275c9b3445e979
2) Command-click on the video
3) Select "Download Video" from the contextual menu

Expected results: The downloaded video has the file extension .mp4

Actual results: The downloaded video has the file extension .gif

As a consequence of this bug, the downloaded video can't be opened. See the attached screenshot. The error dialog says, "It may be damaged or use a file format that Preview doesn't recognize." However, if you simply change the file extension from .gif to .mp4, the video can be played.

The .gif file extension comes from the URL, but URLs are arbitrary and meaningless. They may or may not represent an actual file on the web server; that's a private implementation detail. On the other hand, the HTTP response Content-Type header says the URL is video/mp4.

Both Chrome and Firefox use the .mp4 file extension rather than the .gif file extension when they download the video.

[Radar WebKit Bug Importer]

<rdar://problem/147183354>

[Karl Dubost]

The markup is the same in Safari, Firefox and Chrome

<video class="m-0 max-h-full max-w-full"
       autoplay=""
       playsinline=""
       muted=""
       loop=""
       src="https://external-preview.redd.it/yhb1f6aAABHf5frJUF4mHku3JTgwbg2gl7Wco76dyjA.gif?width=308&amp;format=mp4&amp;s=88a3fadf350d2eb9a9c97192a9275c9b3445e979">
</video>


The response is appropriate for all browsers

```
HTTP/2 206 
content-type: video/mp4
cache-control: public, max-age=604800
server: snooserv-imo
x-imo-features: format=mp4&width=308
via: 1.1 varnish, 1.1 varnish
accept-ranges: bytes
content-range: bytes 0-16082/16083
date: Mon, 17 Mar 2025 05:37:39 GMT
vary: X-Imo-Features,Origin
report-to: {"group": "w3-reporting-nel", "max_age": 14400, "include_subdomains": true,  "endpoints": [{ "url": "https://w3-reporting-nel.reddit.com/reports" }]}, {"group": "w3-reporting", "max_age": 14400, "include_subdomains": true, "endpoints": [{ "url": "https://w3-reporting.reddit.com/reports" }]}, {"group": "w3-reporting-csp", "max_age": 14400, "include_subdomains": true, "endpoints": [{ "url": "https://w3-reporting-csp.reddit.com/reports" }]}
nel: {"report_to": "w3-reporting-nel", "max_age": 14400, "include_subdomains": false, "success_fraction": 0.5, "failure_fraction": 0.5}
content-length: 16083
X-Firefox-Spdy: h2
```

And the "save as" indeed uses the correct file but somehow it picks the URL to determine the filename and the extension for saving the file.
https://external-preview.redd.it/yhb1f6aAABHf5frJUF4mHku3JTgwbg2gl7Wco76dyjA.gif

changing .gif by .mp4 will fix the right result on the finder.

Pull request: https://github.com/WebKit/WebKit/pull/61350

Pull request: https://github.com/WebKit/WebKit/pull/61355

[EWS]

Committed 310122@main (d496d47f982c): <https://commits.webkit.org/310122@main>

Reviewed commits have been landed. Closing PR #61355 and removing active labels.

[EWS]

Committed 305413.592@safari-7624-branch (263ee3956e70): <https://commits.webkit.org/305413.592@safari-7624-branch>

Reviewed commits have been landed. Closing PR #4851 and removing active labels.