Upcoming Firefox release milestones

December 2024
SMTWTFS
1
2
134 b4 GTB
3
4
134 b5 GTB
5
6
134 b7 GTB
135 build ready for nightly QA
7
8
9
134 b8 GTB
SUMO content localization starts
10
11
134 b9 GTB
134 QA sign off
12
13
134 b10 GTB
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
134 go to Build
31
RC

January 2025
SMTWTFS
1
2
135 build ready for beta QA
135 soft Code Freeze starts at 08:00 UTC
3
Final deadline for QA’s Feature Test Plan approval
String Freeze
135 regression testing completed
136 QA request deadline
4
5
6
Merge day
135 b1 GTB
Nightly 136 starts
7
134 Release
8
135 b2 GTB
9
10
135 b3 GTB
SUMO deadline
136 a11y engineering request deadline for Nightly
11
12
13
135 b4 GTB
14
15
135 b5 GTB
16
17
135 b6 GTB
136 build ready for QA
Final deadline for QA’s Feature Test Plan approval
18
19
20
135 b7 GTB
SUMO content localization starts
21
Planned 134.0.x
22
135 b8 GTB
135 QA sign off
23
24
135 b9 GTB
25
26
27
135 go to Build
28
RC
29
30
136 soft Code Freeze starts at 08:00 UTC
31
String Freeze
136 regression testing completed
137 QA request deadline

February 2025
SMTWTFS
1
2
3
Merge day
136 b1 GTB
Nightly 137 starts
4
135 Release
5
136 b2 GTB
6
7
136 b3 GTB
SUMO deadline
137 a11y engineering request deadline for Nightly
8
9
10
136 b4 GTB
11
12
136 b5 GTB
13
14
136 b6 GTB
137 build ready for QA
Final deadline for QA’s Feature Test Plan approval
15
16
17
136 b7 GTB
SUMO content localization starts
18
Planned 135.0.x
19
136 b8 GTB
136 QA sign off
20
21
136 b9 GTB
22
23
24
136 go to Build
25
RC
26
27
137 soft Code Freeze starts at 08:00 UTC
28
String Freeze
137 regression testing completed
138 QA request deadline

March 2025
SMTWTFS
1
2
3
Merge day
137 b1 GTB
Nightly 138 starts
4
136 Release
5
137 b2 GTB
6
7
137 b3 GTB
SUMO deadline
138 a11y engineering request deadline for Nightly
8
9
10
137 b4 GTB
11
12
137 b5 GTB
13
14
137 b6 GTB
138 build ready for QA
Final deadline for QA’s Feature Test Plan approval
15
16
17
137 b7 GTB
SUMO content localization starts
18
Planned 136.0.x
19
137 b8 GTB
137 QA sign off
20
21
137 b9 GTB
22
23
24
137 go to Build
25
RC
26
27
138 soft Code Freeze starts at 08:00 UTC
28
String Freeze
138 regression testing completed
139 QA request deadline
29
30
31
Merge day
138 b1 GTB
Nightly 139 starts

April 2025
SMTWTFS
1
137 Release
2
138 b2 GTB
3
4
138 b3 GTB
SUMO deadline
139 a11y engineering request deadline for Nightly
5
6
7
138 b4 GTB
8
9
138 b5 GTB
10
11
138 b6 GTB
139 build ready for QA
Final deadline for QA’s Feature Test Plan approval
12
13
14
138 b7 GTB
SUMO content localization starts
15
Planned 137.0.x
16
138 b8 GTB
138 QA sign off
17
18
138 b9 GTB
19
20
21
138 go to Build
22
RC
23
24
139 soft Code Freeze starts at 08:00 UTC
25
String Freeze
139 regression testing completed
140 QA request deadline
26
27
28
Merge day
139 b1 GTB
Nightly 140 starts
29
138 Release
30
139 b2 GTB

May 2025
SMTWTFS
1
2
139 b3 GTB
SUMO deadline
140 a11y engineering request deadline for Nightly
3
4
5
139 b4 GTB
6
7
139 b5 GTB
8
9
139 b6 GTB
140 build ready for QA
Final deadline for QA’s Feature Test Plan approval
10
11
12
139 b7 GTB
SUMO content localization starts
13
Planned 138.0.x
14
139 b8 GTB
139 QA sign off
15
16
139 b9 GTB
17
18
19
139 go to Build
20
RC
21
22
140 soft Code Freeze starts at 08:00 UTC
23
String Freeze
140 regression testing completed
141 QA request deadline
24
25
26
Merge day
140 b1 GTB
Nightly 141 starts
27
139 Release
28
140 b2 GTB
29
30
140 b3 GTB
SUMO deadline
141 a11y engineering request deadline for Nightly
31

June 2025
SMTWTFS
1
2
140 b4 GTB
3
4
140 b5 GTB
5
6
140 b6 GTB
141 build ready for QA
Final deadline for QA’s Feature Test Plan approval
7
8
9
140 b7 GTB
SUMO content localization starts
10
Planned 139.0.x
11
140 b8 GTB
140 QA sign off
12
13
140 b9 GTB
14
15
16
140 go to Build
17
RC
18
19
141 soft Code Freeze starts at 08:00 UTC
20
String Freeze
141 regression testing completed
142 QA request deadline
21
22
23
Merge day
141 b1 GTB
Nightly 142 starts
24
140 Release
25
141 b2 GTB
26
27
141 b3 GTB
SUMO deadline
142 a11y engineering request deadline for Nightly
28
29
30
141 b4 GTB

July 2025
SMTWTFS
1
2
141 b5 GTB
3
4
141 b6 GTB
142 build ready for QA
Final deadline for QA’s Feature Test Plan approval
5
6
7
141 b7 GTB
SUMO content localization starts
8
Planned 140.0.x
9
141 b8 GTB
141 QA sign off
10
11
141 b9 GTB
12
13
14
141 go to Build
15
RC
16
17
142 soft Code Freeze starts at 08:00 UTC
18
String Freeze
142 regression testing completed
143 QA request deadline
19
20
21
Merge day
142 b1 GTB
Nightly 143 starts
22
141 Release
23
142 b2 GTB
24
25
142 b3 GTB
SUMO deadline
143 a11y engineering request deadline for Nightly
26
27
28
142 b4 GTB
29
30
142 b5 GTB
31

August 2025
SMTWTFS
1
142 b6 GTB
143 build ready for QA
Final deadline for QA’s Feature Test Plan approval
2
3
4
142 b7 GTB
SUMO content localization starts
5
Planned 141.0.x
6
142 b8 GTB
142 QA sign off
7
8
142 b9 GTB
9
10
11
142 go to Build
12
RC
13
14
143 soft Code Freeze starts at 08:00 UTC
15
String Freeze
143 regression testing completed
144 QA request deadline
16
17
18
Merge day
143 b1 GTB
Nightly 144 starts
19
142 Release
20
143 b2 GTB
21
22
143 b3 GTB
SUMO deadline
144 a11y engineering request deadline for Nightly
23
24
25
143 b4 GTB
26
27
143 b5 GTB
28
29
143 b6 GTB
144 build ready for QA
Final deadline for QA’s Feature Test Plan approval
30
31

September 2025
SMTWTFS
1
143 b7 GTB
SUMO content localization starts
2
Planned 142.0.x
3
143 b8 GTB
143 QA sign off
4
5
143 b9 GTB
6
7
8
143 go to Build
9
RC
10
11
144 soft Code Freeze starts at 08:00 UTC
12
String Freeze
144 regression testing completed
145 QA request deadline
13
14
15
Merge day
144 b1 GTB
Nightly 145 starts
16
143 Release
17
144 b2 GTB
18
19
144 b3 GTB
SUMO deadline
145 a11y engineering request deadline for Nightly
20
21
22
144 b4 GTB
23
24
144 b5 GTB
25
26
144 b6 GTB
145 build ready for QA
Final deadline for QA’s Feature Test Plan approval
27
28
29
144 b7 GTB
SUMO content localization starts
30
Planned 143.0.x

October 2025
SMTWTFS
1
144 b8 GTB
144 QA sign off
2
3
144 b9 GTB
4
5
6
144 go to Build
7
RC
8
9
145 soft Code Freeze starts at 08:00 UTC
10
String Freeze
145 regression testing completed
146 QA request deadline
11
12
13
Merge day
145 b1 GTB
Nightly 146 starts
14
144 Release
15
145 b2 GTB
16
17
145 b3 GTB
SUMO deadline
146 a11y engineering request deadline for Nightly
18
19
20
145 b4 GTB
21
22
145 b5 GTB
23
24
145 b6 GTB
146 build ready for QA
Final deadline for QA’s Feature Test Plan approval
25
26
27
145 b7 GTB
SUMO content localization starts
28
Planned 144.0.x
29
145 b8 GTB
145 QA sign off
30
31
145 b9 GTB

November 2025
SMTWTFS
1
2
3
145 go to Build
4
RC
5
6
146 soft Code Freeze starts at 08:00 UTC
7
String Freeze
146 regression testing completed
147 QA request deadline
8
9
10
Merge day
146 b1 GTB
Nightly 147 starts
11
145 Release
12
146 b2 GTB
13
14
146 b3 GTB
SUMO deadline
147 a11y engineering request deadline for Nightly
15
16
17
146 b4 GTB
18
19
146 b5 GTB
20
21
146 b6 GTB
147 build ready for QA
Final deadline for QA’s Feature Test Plan approval
22
23
24
146 b7 GTB
SUMO content localization starts
25
Planned 145.0.x
26
146 b8 GTB
146 QA sign off
27
28
146 b9 GTB
29
30

December 2025
SMTWTFS
1
146 go to Build
2
RC
3
4
147 soft Code Freeze starts at 08:00 UTC
5
String Freeze
147 regression testing completed
6
7
8
Merge day
147 b1 GTB
9
146 Release
10
147 b2 GTB
11
12
147 b3 GTB
SUMO deadline
13
14
15
147 b4 GTB
16
17
147 b5 GTB
18
Planned 146.0.x
19
147 b6 GTB
20
21
22
147 b7 GTB
SUMO content localization starts
23
24
147 b8 GTB
147 QA sign off
25
26
147 b9 GTB
27
28
29
30
31

January 2026
SMTWTFS
1
2
3
4
5
147 go to Build
6
RC
7
8
9
10
11
12
13
147 Release
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Planned 147.0.x
28
29
30
31