Stephen Shankland/CNET

Twitter has raised its limit on photo quality, now preserving fine details it had previously scrubbed out in an effort to cut down on file sizes and make the service faster to use. The change lets you zoom into photos better if your own screen is big enough to take advantage of the new detail that's possible.

Twitter programmer Nolan O'Brien announced the change in a Tuesday tweet thread. The change only applies to images uploaded through the Twitter website, O'Brien and a Twitter representative said. And you'll likely only see it when you click on a photo to view it large. The move follows an increase in Twitter's maximum viewable photo size from 4 megapixels to 16 megapixels that began with Twitter for the web in 2018 and that's now spread to Twitter for iPads and the Twitter Mac app.

People are most likely to view and interact with tweets that have audio, video and photos, Twitter said in a statement. The most recent change means people can do all that "without having to sacrifice the quality of what they're sharing."

Tweaking photos may sound like a minor improvement, but it can be important. You might flick past many ho-hum photos, but every pixel can count when you want to dive into a lovely landscape, gawk at a closeup of an otherworldly arthropod or scrutinize a leaked product photo to try to figure out if it's real or fake.

O'Brien kicked off his tweet with a 4,096x4,096 pixel photo of bright red autumn leaves. Previously, Twitter would recompress images using a technique called chroma subsampling that can smear color details -- particularly with red -- when you zoom in. On top of that, Twitter would perform the compression twice, once when you uploaded the photo and a second time when Twitter would store the shot in its back-end database.

Starting today, Twitter will preserve JPEGs as they are encoded for upload on Twitter for Web. (Caveat, cannot have EXIF orientation)



For example: the attached photo is actually a guetzli encoded JPEG at 97% quality with no chroma subsampling.https://t.co/1u37vTopkY pic.twitter.com/Eyq67nfM0E — Nolan O'Brien (@NolanOBrien) December 11, 2019

Twitter now preserves your JPEG photo's original compression settings. His example JPEG image had been encoded with Google's Guetzli compression technology, which is slow to use but shrinks file sizes compared to typical JPEG photos. When you're actually looking at photos, most of the time you'll likely see a Twitter-compressed version, for example the 680-pixel-wide shot created for viewing in the timeline. But you'll see the original if you click or tap on it using Twitter for the web or using the Twitter app for iPads or Macs.

Next year, Twitter also will bring the same image-quality improvement to profile photos, though they'll remain 400x400 pixels in size, and to the 1,500x500 pixel banner photo you can put on your profile page.

It's also possible that Twitter will lift photo-size upload limits for people using the Twitter apps for Android, iOS and iPadOS. Currently, those shots are compressed and resized to a maximum of 2,048x2,048 pixels.

And Twitter will recompress photos larger than 4,096x4,096 pixels or 5MB in size. "Images are not unbounded in file size or resolution, but those limits are very generous," O'Brien said.

Indeed, a maximum of 4,096x4,096 is a significant step above Facebook, which limits photo width to 2,048 pixels, and its photo-sharing service Instagram, which caps photos at a maximum of 1,080 pixels wide and 1,350 pixels tall. At SmugMug's Flickr photo-sharing service, the maximum width shown is 2,048 pixels, but Flickr shows pro members' shots at 6,144 pixels as long as viewers are using a screen with high enough resolution.

First published Dec. 11.

Correction, Dec. 12: Twitter started showing 16-megapixel images in 2018. The new change concerns compression settings that now preserve photo detail better.