The AI approach is interesting but there are just too many problems with it.
MozJPEG is actually using something similar called trellis quantization or soft-thresholding. The idea is to further quantize DCT coefficients in noisy areas. There are some limitations [1] though. But it's not an issue with locally sensitive metrics and can be improved with edge detection.
Another challenge here is to estimate the current image quality and the target error.
[1] https://github.com/mozilla/mozjpeg/issues/129
In Faster Images using HTTP2 and Progressive JPEGsmozilla
mozjpeg
C2014–2025
mozilla / mozjpeg
mozjpeg
Improved JPEG encoder.
24Distinct people
28Mentions
0Explicit recommenders
5.7KGitHub stars
What to know before exploring
What it is
Improved JPEG encoder.
GitHub
Where it is used
No documented product use was verified in the last source check.
What people are saying
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Also in these discussions
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This week on Hacker News
Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 2:17:07 AM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year28 dated mentions
Observed mentions: 2014-03-05 19:17:44 UTC to 2025-10-22 18:18:42 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2014 | 2014-01-01 00:00:00 UTC | 2015-01-01 00:00:00 UTC | 6 | 2 | 4 |
| 2015 | 2015-01-01 00:00:00 UTC | 2016-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2016 | 2016-01-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 5 | 1 | 4 |
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 4 | 0 | 4 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 5 | 0 | 5 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 1 | 0 | 1 |
From the project README
An excerpt from the repository, fetched Nov 13, 2026.
Read the project’s introduction
Mozilla JPEG Encoder Project
MozJPEG improves JPEG compression efficiency achieving higher visual quality and smaller file sizes at the same time. It is compatible with the JPEG standard, and the vast majority of the world's deployed JPEG decoders.
MozJPEG is a patch for libjpeg-turbo. Please send pull requests to libjpeg-turbo if the changes aren't specific to newly-added MozJPEG-only compression code. This project aims to keep differences with libjpeg-turbo minimal, so whenever possible, improvements and bug fixes should go there first.
MozJPEG is compatible with the libjpeg API and ABI. It is intended to be a drop-in replacement for libjpeg. MozJPEG is a strict superset of libjpeg-turbo's functionality. All MozJPEG's improvements can be disabled at run time, and in that case it behaves exactly like libjpeg-turbo.
MozJPEG is meant to be used as a library in graphics programs and image processing tools. We include a demo cjpeg command-line tool, but it's not intended for serious use. We encourage authors of graphics programs to use libjpeg's C API and link with MozJPEG library instead.
Features
Progressive encoding with "jpegrescan" optimization. It can be applied to any JPEG file (with jpegtran) to losslessly reduce file size.
Trellis quantization. When converting other formats to JPEG it maximizes quality/filesize ratio.
Comes with new quantization table presets, e.g. tuned for high-resolution displays.
Fully compatible with all web browsers.
Can be seamlessly integrated into any program that uses the industry-standard libjpeg API. There's no need to write any MozJPEG-specific integration code.
Releases
Latest release
Overview of 3.0 features
Version 2.0 Announcement
Version 1.0 Announcement
Compiling
See BUILDING. MozJPEG is built exactly the same way as libjpeg-turbo, so if you need additional help please consult libjpeg-turbo documentation.
Read the full README on GitHubWhat Hacker News says
5 sourcesHow does this compare to mozjpeg [1] ?
[1] https://github.com/mozilla/mozjpeg
In Guetzli – Google's new “zopfli-like” JPEG encoderHas anybody tried mozjpeg? https://github.com/mozilla/mozjpeg
It works much better than any of the alternatives listed here, I'm surprised noone mentioned it yet.
Here is an image compressed to the same size with
mozjpeg http://m8y.org/hn/12597098.jpeg
jpeg.io http://i.pi.gy/AP8v.jpg
In Show HN: Jpeg.io – Convert any major image format into a highly optimized JPEGIt looks like this binary searches across the Go quality levels to find acceptable quality. This isn't a bad idea, but it won't be fruitful. The Go standard library JPEG encoder is pretty basic, and reuses the quant tables from the spec. It also doesn't optimize the huffman tables, so the pics are typically 10% bigger than they need to be.
This idea, taken to the extreme is mozjpeg. It is really advanced and can take advantage of a lot of cool tricks (like trellis optimization) in order to get the absolute best quality for the size.
https://github.com/mozilla/mozjpeg
In Show HN: Smlr – re-encode jpegs using butteraugli visual quality measurement