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og:image preview bails out if Content-Length header is missing, many image CDNs use streaming or chunked encoding now #6645

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jonsherrard opened this issue Oct 18, 2023 · 2 comments · May be fixed by #7046
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og:image preview bails out if Content-Length header is missing, many image CDNs use streaming or chunked encoding now #6645

jonsherrard opened this issue Oct 18, 2023 · 2 comments · May be fixed by #7046
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@jonsherrard
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  • I have searched open and closed issues for duplicates
  • I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

Bug Description

Steps to Reproduce

  1. step one
    Open a chat
  2. step two
    Paste https://vercel.com/docs/functions/edge-functions/og-image-generation
  3. step three
    Notice there is no OG image loaded.

Actual Result:

No image preview is laoded in the chat is because vercel's image servers don't set a content-length, so it bails out:

Signal-Desktop/ts/linkPreviews/linkPreviewFetch.ts

Line 539 in 172598b

if (contentLength > MAX_IMAGE_CONTENT_LENGTH) {

Expected Result:

The image preview should load.

Screenshots

Signal:
image

Other chat app:
image

Platform Info

Signal Version:

6.34.1
production (Apple silicon)

Operating System:

14.0 (23A344)

Linked Device Version:
@der-eismann
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der-eismann commented Oct 9, 2024 •
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We just stumbled upon the same issue with our website, where we serve images from CloudFront with compression enabled. Since CloudFront dismisses the Content-Length header on compressed requests, we are not getting any preview images.
Would be great if we could find a solution for this, especially since the mobile app is not affected by this.

FTR these are the headers served by CloudFront:

< HTTP/2 200 
< content-type: image/jpeg
< date: Wed, 09 Oct 2024 16:49:57 GMT
< cache-control: max-age=315360000,public
< etag: "3b0c79e2613…"
< expires: Sat, 07 Oct 2034 16:49:57 GMT
< vary: Accept
< x-cache: Miss from cloudfront
< via: 1.1 ….cloudfront.net (CloudFront)
< x-amz-cf-pop: …
< alt-svc: h3=":443"; ma=86400
< x-amz-cf-id: skD88pp1R…

@der-eismann der-eismann linked a pull request Oct 10, 2024 that will close this issue
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@ryan-williams
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ryan-williams commented Apr 29, 2025 •
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This issue has driven me crazy, for years(?). OG images for my sites are frequently broken on Signal macOS and Android.

I hope someone reviews #7046 soon, it's been open for over 6 months. cc @scottnonnenberg-signal.

Here's a simple example: https://runsascoded.s3.amazonaws.com/og/test1.html. The og:image works in every service I've tried:

Facebook/X/LinkedIn/Discord ✅

c/o opengraph.xyz:

Screenshot 2025-04-29 at 1 31 12 AM

WhatsApp ✅ image
Slack ✅

image

but Signal Desktop or Android are broken ❌:

Image

Last time I hit this (signalapp/Signal-iOS#5559 (comment)), switching PNG to JPG fixed it for some reason, but that's not working for me this time.

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Load og:image preview even if Content-Length header is missing der-eismann/Signal-Desktop
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@ryan-williams @jonsherrard @der-eismann @ayumi-signal