What's the best AV1 encoder in 2025? I encoded four thousand GIFs to find out.
What’s the best AV1 encoder in 2025?
By “best” I mean, I guess, compression/quality ratio. I don’t really care that much about compute intensity since I’m not transcoding.
I found empirical evidence in this area lacking. This post is my attempt to inform on that subject.
AVIF is the new JPG?
AV1 Image File Format (AVIF) is a powerful, open source, royalty-free file format that encodes AV1 bitstreams in the High Efficiency Image File Format (HEIF) container.
- mdn web docs
“Wait, I thought AV1 was for video?”
You are correct! But what is a video, exactly? A series of images with or without accompanying audio? AVIF is essentially just AV1-encoded images, wrapped into an “HEIF” (high-efficiency image file) container (a fancy way to store a series of images).
What you need to understand is that AVIF is simply a new image file format, like PNG, JPG, and WEBP. According to caniuse1, AVIF is supported in all evergreen browsers since January 2024. That means the answer to “can I use AVIF?” is “yes!”
But which encoder?
There are currently three open source AV1 encoders: Libaom, SVT-AV1, and rav1e. Libaom is a “reference implementation” and is generally reliable, but really shouldn’t be used. SVT-AV1 is an “open-source encoder and decoder developed primarily by Intel in collaboration with Netflix”2. rav1e calls itself “The fastest and safest AV1 encoder”3 and it’s written in Rust if that means anything to you.
Test 1: One small GIF for man, one (much) smaller AVIF for mankind
I took a simple 88x31 animated GIF I created for catskull.net and used ffmpeg to convert it to an .avif with all three encoders. The exact command I used is: ffmpeg -i badge.gif -c:v $ENCODER badge.avif, where $ENCODER is the value from the table below.
| encoder | file size | compression ratio | savings | file |
|---|---|---|---|---|
| gif | 648 KB | 1 | 0% |  |
libaom-av1 |
41 KB | 13.5 | 92.59% |  |
librav1e |
16 KB | 40.5 | 97.53% |  |
libsvtav1 |
15 KB | 43.2 | 97.69% |  |
SVT-AV1 is the clear winner in this shootout, though rav1e is a good option as well. There may be additional parameters we could tweak to get more performance out of each respective encoder, but without guidance I don’t know how to do it and I sure as heck don’t trust LLM to hallucinate ffmpeg commands!
Test 2: Four Thousand Gifs
I decided to take an online button collection over at cyber.dabamos.de and encode them all in avif. The collection has 4,539 images. After encoding them all to avif, I compressed the directory of gifs and the directory of avifs into zip files and this is the result. I suppose that this is a decent look at savings “on average”. The exact command I used is parallel ffmpeg -i {} -c:v $ENCODER "../$ENCODER/{.}.avif" ::: *.gif, where $ENCODER is the value from the table below. Note parallel can be installed with brew, and it will max out your CPU by default.
| encoder | zip file size | compression ratio | savings |
|---|---|---|---|
| gif | 32.3 MB | 1 | 0% |
libaom-av1 |
27.7MB | 1.1661 | 14.24% |
librav1e |
22.8 MB | 1.4167 | 29.41% |
libsvtav1 |
19.9 MB | 1.6231 | 38.39% |
Unfortunately not quite the silver-bullet the test above presented, but still, that’s free bandwidth baby! On further investigation, it seems like the minimum file size for our avif is 1 KB. Looking in the source GIF directory, there are quite a few that are less than 1 KB. I’m not sure if this is due to the the container image itself, but I guess if your GIF is less than 1 KB then you probably don’t need to bother encoding it.
View the buttons at buttons.catskull.net!
Test 3: A WebM video
Since I love this zone plate animation I love so much, I like to use it in lots of places. I have previously used webm as my standard for this kind of thing, but let’s give avif a shot! I screen captured the animation I generated on shadertoy and converted to a webm. I will compare against avif, gif, and apng.
Except for the avif encoders, I ran the following command:
ffmpeg -i zoneplate.webm zoneplate.$IMAGE_TYPE, where image type is from the table below.
| image type | file size | compression ratio | savings |
|---|---|---|---|
| webm | 859 KB | 1 | 0% |
| apng | 138 MB | 0.0062 | -15,965.19% |
| gif | 23.5 MB | 0.0366 | -2,635.74% |
libsvtav1 |
114 KB | 7.5351 | 86.73% |
libaom-av1 |
89 KB | 9.6517 | 89.64% |
librave1e |
85 KB | 10.1059 | 90.1% |
Quite different results again! I’m not sure what’s up with apng, but I opened the file in iina and it played just fine. This time, STV-AV1 was behind both Libaom and rav1e by about 3 points!
Here are the resulting images (gif and apng excluded).
webm (859 KB):
libsvtav1 (114 KB):
libaom-av1 (89 KB):
librav1e (85 KB):
It seems like in all cases, avif has a hard time playing a consistent framerate in both Safari 18.5 and Safari Technology Preview Release 219. The issue does not present in Chromium 136.0.7103.113 (ungoogled-chromium).
Conclusion
Based on my testing, I believe that rav1e is currently the most reliable encoder. It’s not a night and day difference in most cases. In some cases, SVT-AV1 offered smaller files, but in our webm test, it performed much worse than both rav1e and Libaom, which is suprising considering that Libaom took last place in every other test, as we would expect.
In either case, using avif instead of any other image format is recommended. We have mainline support in all evergreen browsers. The bandwidth savings can be up to 97%! It feels a bit like switching out an incandescent light bulb for a new-fangled LED bulb. It’s free real estate!
Be sure to check out the gallery at buttons.catskull.net!
