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mozilla
mozjpeg
C2014–2025
mozilla / mozjpeg

mozjpeg

Improved JPEG encoder.

Web DevelopmentCreative & MediaScience & Engineering
Explore on GitHubRead Hacker News discussions
24Distinct people
28Mentions
0Explicit recommenders
5.7KGitHub stars
REPOSITORY AT A GLANCE

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

No recommendation phrase was found in the indexed comments.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 12:45:45 PM 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.

02462014-01-01 00:00:00 UTC to 2015-01-01 00:00:00 UTC (exclusive): 6 mentions; 2 submissions, 4 comments20142015-01-01 00:00:00 UTC to 2016-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2016-01-01 00:00:00 UTC to 2017-01-01 00:00:00 UTC (exclusive): 5 mentions; 1 submissions, 4 comments2017-01-01 00:00:00 UTC to 2018-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2018-01-01 00:00:00 UTC to 2019-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments20192020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 4 mentions; 0 submissions, 4 comments2023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 5 mentions; 0 submissions, 5 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2025

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20142014-01-01 00:00:00 UTC2015-01-01 00:00:00 UTC624
20152015-01-01 00:00:00 UTC2016-01-01 00:00:00 UTC101
20162016-01-01 00:00:00 UTC2017-01-01 00:00:00 UTC514
20172017-01-01 00:00:00 UTC2018-01-01 00:00:00 UTC101
20182018-01-01 00:00:00 UTC2019-01-01 00:00:00 UTC000
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC000
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC101
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC202
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC404
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC505
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC202
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC101

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 GitHub

What Hacker News says

2 sources
wojtek1942·May 20, 2024
It took a bit of time for me to respond because I wanted to make sure I wrote down the info in a nice detailed way. I will update the descriptions on the website to include the information I am proving here to give visitors a better understanding of the options. To be clear, I am not an expert on all this image coding stuff. I just wanted to make a simple tool to let people try out Jpegli because I thought it was interesting even though I don't know so much about the topic. Progressive Rendering There are 3 options on the website. None, Basic and Enhanced. There correspond respectively to options 0, 1 and 2 for the JXL_ENC_FRAME_SETTING_PROGRESSIVE_DC option [1]. "Set the progressive mode using lower-resolution DC images for VarDCT. Use -1 for the encoder default, 0 to disable, 1 to have an extra 64x64 lower resolution pass, 2 to have a 5
Read the rest
12x512 and 64x64 lower resolution pass." So "Basic" provides 1 scan and "Enhanced" provides 2 scans. Here is a detailed description on progressive loading: https://www.thewebmaster.com/progressive-jpegs/ DCT Method I can't really find documentation about DTC Method in libjxl but the options seems to be very similar to the options offered in mozjpeg [2]. They have a detailed explanation on that page I referenced which I won't all copy here. Seems like slow integer is the preferred method as the others are marked as legacy. Maybe I should just remove the options? From my testing the slow integer method has slightly worse compression but it is accurate. XYB colorspace TBH, the library I am using only supports a few color spaces and it does not include XYB and I have not looked into it much further. Also as you can see I did not really bother to add colorspace settings in general but I might do it later. [1] https://libjxl.readthedocs.io/en/latest/api_encoder.html#_CP... [2] https://github.com/mozilla/mozjpeg/blob/6c9f0897afa1c2738d72...
In Show HN: I built an image optimization tool based on Google's new Jpegli encoder

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