By default, Bluesky will serve you two types of sample versions: feed_thumbnail and feed_fullsize. These are not the best publicly available versions on the site. In order to access a higher-quality version, you need to reformat the URL to retrieve the original blob version instead. This requires changing the URL to include the user's DID (decentralized identifier), but performing this process manually every time is awful. Instead, you should use a userscript linked to in the Bluesky entry of our Sites and Sources wiki pages:

Bluesky entry in the Sites and Sources pages: https://e621.net/wiki_pages/31895#bluesky
Bluesky redirect userscript: https://gist.github.com/Tarrgon/a58375cd3c1f15d8fd4238a2a7df35b5

In order to use userscripts, you will need a userscript manager. An example of a userscript manager is Tampermonkey: https://www.tampermonkey.net/
Once you install a userscript manager extension of your choice, copy-paste the script linked above into a new script and save. All Bluesky image links will now reload to the higher-quality blob version. The quality improvement will vary from virtually imperceptible to significantly less JPEG compression, but this version will always be superior.

We currently have ~55 pages of potential Bluesky replacements at 250 posts per page. Using the script will prevent your future Bluesky posts from being replaced and ensures that we can preserve the best-quality public versions from the site.

08/05/2025 edit:

We now also have a userscript to convert Bluesky account and post pages to use more permanent DID numbers, available here:
https://gist.github.com/Tarrgon/c84f267a4f97314090b4870760b8fb8f

Currently, a username change can result in broken links due to Bluesky treating usernames as part of the post identifier. Compare the following:
https://bsky.app/profile/quantamagazine.bsky.social
https://bsky.app/profile/did:plc:vfktz6qe6vy7serr3wqutpzt

Both of these links lead to the same page, but only the second will remain valid if an individual or organization changes its social media name or associated domain. The DID link version is a more stable solution for including in source fields, avoiding but not eliminating the risk of link rot, while remaining a primary source (Wayback Machine is invaluable, but technically a third-party source).

Wayback Machine links to the above scripts in the event that the GitHub pages are unavailable in the future:
Sample-to-original-blob
Username-to-DID-links

I checked this a few days ago and smiled when I found out only like a 1/5th of bsky posts are sourced from that API endpoint.

Sometimes I wondered if it was possible to add a feature to the upload page to enter the URL of the post and it would extract the best possible image URL associated with the post automatically...

aninox said:
Sometimes I wondered if it was possible to add a feature to the upload page to enter the URL of the post and it would extract the best possible image URL associated with the post automatically...

Danbooru has this but multiple successive e6 devs have denied implementing it due to how complicated it can be to upkeep

Maybe the BlueSky developer should be approached about being able to conveniently retrieve the image file you want to download

nin10dope said:
Maybe the BlueSky developer should be approached about being able to conveniently retrieve the image file you want to download

Like its predecessor Twitter/X or any other social media site, Bluesky is not designed as an art gallery or a file-sharing service.
Everything is compressed to shit and more, and artists should instead be persuaded to post elsewhere if they want to retain their artwork quality.

The setup is quite a bit more complex than installing a simple userscript, but you can also use FoxTrove to scrape the best available versions from Bluesky (and many other sites), then automatically reverse-search each one to identify posts that could potentially be replaced.

thegreatwolfgang said:
Like its predecessor Twitter/X or any other social media site, Bluesky is not designed as an art gallery or a file-sharing service.
Everything is compressed to shit and more, and artists should instead be persuaded to post elsewhere if they want to retain their artwork quality.

Yeahhhh you made me remember Facebook utterly nuking everything posted there
At least Messenger doesn't commit war crimes on images sent through it