Releases

Current Releases

Standard support

Based on Gecko 149

Firefox 149.0
Based on Gecko 149

Released on 2026-03-24

SeaMonkey 2.146
Based on Gecko 149

Released on TBD

Based on Gecko 38

Thunderbird 60.89
Based on Gecko 60

Released on 2026-03-24

Based on Gecko 28

Firefox OS 1.3
Based on Gecko 28

Released on 2014-03-17

Extended support

Based on Gecko 60

Firefox 60.89.0esr
Based on Gecko 60

Released on 2026-03-24

Upcoming Releases

NOTE: The dates listed in this section refer to the date of the code merge, not the date of release. See the branch migration calendar for more information.

Based on Gecko 150

Firefox 150
Based on Gecko 150

Currently in BETA channel
Moves to RELEASE week of April 21, 2026

Thunderbird 150
Based on Gecko 150

Currently in BETA channel

SeaMonkey 2.147
Based on Gecko 150

Currently in BETA channel
Moves to RELEASE week of April 21, 2026

Based on Gecko 54

Firefox 54
Based on Gecko 54

Currently in AURORA channel
Moves to BETA week of April 21, 2026

Thunderbird 54
Based on Gecko 54

Currently in EARLYBIRD channel
Moves to BETA week of April 21, 2026

SeaMonkey 2.51
Based on Gecko 54

Currently in AURORA channel
Moves to BETA week of April 21, 2026

Based on Gecko 151

Firefox 151
Based on Gecko 151

Currently in NIGHTLY channel
Moves to BETA week of April 21, 2026

Thunderbird 151
Based on Gecko 151

Currently in DAILY channel
Moves to BETA week of April 21, 2026

SeaMonkey 2.148
Based on Gecko 151

Currently in NIGHTLY channel
Moves to AURORA week of April 21, 2026

B2G Releases

Firefox OS 1.4
Based on Gecko 30

Released on ??

Firefox OS 2.0
Based on Gecko 32

Currently in BETA channel
Moves to RELEASE week of ??

Firefox OS 2.1
Based on Gecko 34

Currently in AURORA channel
Moves to BETA week of ??

Firefox OS 2.2
Based on Gecko 37

Currently in NIGHTLY channel
Moves to AURORA week of ??

Previous Releases

More details of the RapidRelease Calendar

2015

Release	Date	Notes
SeaMonkey 2.35	September 3	Release Notes
Firefox 40.0.3	August 27	Release Notes
Thunderbird 38.2.0	August 14	Release Notes
Firefox 40.0.2	August 13	Release Notes
Firefox 40	August 11	Release Notes
Firefox 39.0.3	August 6	Release Notes
Thunderbird 31.8.0	July 17	Release Notes
Thunderbird 38.1.0	July 9	Release Notes
Firefox 39	July 02	Release Notes
Thunderbird 38.0.1	June 11	Release Notes
Firefox 38.0.5	June 2	Release Notes
Thunderbird 31.7.0	May 12	Release Notes
Firefox 38.0.1	May 14	Release Notes
Firefox 38	May 12	Release Notes
Firefox 37.0.2	April 20	Release Notes
Firefox 37.0.1	April 3	Release Notes
Thunderbird 31.6.0	March 31	Release Notes
Firefox 37	March 31	Release Notes
SeaMonkey 2.33.1	March 23	Release Notes
Firefox 36.0.4	March 21	Release Notes
Firefox 36.0.3	March 20	Release Notes
SeaMonkey 2.33	March 10	Release Notes
Firefox 36.0.1	March 5	Release Notes
Thunderbird 31.5.0	February 24	Release Notes
Firefox 36.0	February 24	Release Notes
SeaMonkey 2.32	January 13	Release Notes
Thunderbird 31.4.0	January 13	Release Notes
Firefox 35.0	January 13	Release Notes

2014 and earlier

For releases prior to 2015, see the archive.

Other Links

This is a page for tracking in-progress releases. For maintenance releases, we use a general checklist to ensure we don't miss anything.

• perhaps you'd like to see who release drivers for various releases are?
• or perhaps you'd like to learn more about the priority rankings we assign to releases?
• you might even wonder how we use flags to manage our releases?
• or what branches exist and when they branched?
• perchance you're confused about update terminology?
• maybe you'd like to know about our various branch support levels?
• perhaps you want to see the RapidRelease Calendar for future aurora merges, beta merges, and releases?
• maybe you are interested in checking the Feature Release Tracker for upcoming features?