Talk:Mozilla Firefox

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Criticising mozLZ4.

I don't think this is relevant enough for the article's main page, therefore I am posting it here.
If I ever need to explain how disadvantageous LZ4 is, I can always refer them over here.

I am not implying the comperssion algorithm Lz4 is bad. But adding an Lz4 layer to JSON files was a terrible idea by Mozilla.

Since Firefox version 56 (which is the last non-quantum version of Firefox), the session files in the 📁 sessionstore-backups directory are no longer recovery.bak and recovery.json, but recovery.baklz4 and recovery.jsonlz4. They should have called it recovery.bak.lz4 and recovery.json.lz4, which would be more logical file names, but they should not have done it in first place. Also the folders 📁bookmarkbackups 📁crashes/store.json.mozlz4 📁datareporting is affected (intoxicated) by Lƶ4.

“If it isn't broken, don't ‘fix’ it” does not apply to everything (e.g. when improving something), but to this one, it certainly does apply.

Previously, Firefox session backups were stored in plain text (just like places.sqlite). But Firefox 56, released on 20170612, added LZ4 bulk, that made recovering lost sessions harder and more time-consuming to me. Some tools that were supposed to decode LZ4 did not work.

There is a lz4 scrounger by a GitHub user called Jscher2000 (Jefferson Scher), which is supposed to turn the “LZ4” information into plain text, but that one does not work properly and crashes the tab.

At least, LZ4 does not erase information without warning like Google Chrome/Chromium did with Version 37 (20140905): removing ArchivedHistory file.


Semi-Advantages of LZ4

  • Slightly saves some disk space storage.
    • How much does it save? 10 MB? Are we in 1990?! 100MB? Are we in 2000? Even if plain text files instead of cost me 1 GB, I'd rather have 1 GB of disk storage reserved for it instead of LZ4. And modern file systems (including ext2, ext3, ext4, btrFS, NTFS, ZFS) offer transparent compression functionality. We are in 2019. Why not compress browser cache altogether? Invalid upside.
    • Save ⭐🌟10 seconds(!)🌟⭐ when doing a backup of the .mozilla or profile folder. Hooray! ̶A̶̶w̶̶e̶̶s̶̶o̶̶m̶̶e̶!

LZ4 Disadvantages

LZ4's disadvantages outweigh the (nearly non-existent advantages.
When web-searching “LZ4”, the reasons for why only negative things and complaints come up is obvious. LZ4 was an unnecessary misstep exactly nobody asked for.

  • Incompatible to all previous Firefox versions.
    • Firefox ≥56 is also not backwards-compatible to the plain-text format.
  • Harder to find retreive information from damaged media.
  • Unsuitable for text/JSON editors.
  • More CPU usage (although marginial. LZ4 is efficient and fast, but not as much as plain text).


There is absolutely no need for LZ4.
It does more harm than good.