This is a staging environment for whattrainisitnow.com

Upcoming Firefox release milestones

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
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
Potential mobile 142.0.x
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
Potential mobile 143.0.x
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
Potential mobile 144.0.x
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
Potential mobile 145.0.x
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
148 QA request deadline
6
7
8
Merge day
147 b1 GTB
Nightly 148 starts
9
146 Release
10
147 b2 GTB
11
12
147 b3 GTB
SUMO deadline
148 a11y engineering request deadline for Nightly
13
14
15
147 b4 GTB
16
Potential mobile 146.0.x
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
25
26
148 build ready for QA
Final deadline for QA’s Feature Test Plan approval
27
28
29
147 b8 GTB
147 QA sign off
30
31
147 b9 GTB

January 2026
SMTWTFS
1
2
3
4
5
147 go to Build
6
RC
7
8
148 soft Code Freeze starts at 08:00 UTC
9
String Freeze
148 regression testing completed
149 QA request deadline
10
11
12
Merge day
148 b1 GTB
Nightly 149 starts
13
147 Release
14
148 b2 GTB
15
16
148 b3 GTB
SUMO deadline
149 a11y engineering request deadline for Nightly
17
18
19
148 b4 GTB
20
Potential mobile 147.0.x
21
148 b5 GTB
22
23
148 b6 GTB
149 build ready for QA
Final deadline for QA’s Feature Test Plan approval
24
25
26
148 b7 GTB
SUMO content localization starts
27
Planned 147.0.x
28
148 b8 GTB
148 QA sign off
29
30
148 b9 GTB
31

February 2026
SMTWTFS
1
2
148 go to Build
3
RC
4
5
149 soft Code Freeze starts at 08:00 UTC
6
String Freeze
149 regression testing completed
150 QA request deadline
7
8
9
Merge day
149 b1 GTB
Nightly 150 starts
10
148 Release
11
149 b2 GTB
12
13
149 b3 GTB
SUMO deadline
150 a11y engineering request deadline for Nightly
14
15
16
149 b4 GTB
17
Potential mobile 148.0.x
18
149 b5 GTB
19
20
149 b6 GTB
150 build ready for QA
Final deadline for QA’s Feature Test Plan approval
21
22
23
149 b7 GTB
SUMO content localization starts
24
Planned 148.0.x
25
149 b8 GTB
149 QA sign off
26
27
149 b9 GTB
28

March 2026
SMTWTFS
1
2
149 go to Build
3
RC
4
5
150 soft Code Freeze starts at 08:00 UTC
6
String Freeze
150 regression testing completed
151 QA request deadline
7
8
9
Merge day
150 b1 GTB
Nightly 151 starts
10
149 Release
11
150 b2 GTB
12
13
150 b3 GTB
SUMO deadline
151 a11y engineering request deadline for Nightly
14
15
16
150 b4 GTB
17
Potential mobile 149.0.x
18
150 b5 GTB
19
20
150 b6 GTB
151 build ready for QA
Final deadline for QA’s Feature Test Plan approval
21
22
23
150 b7 GTB
SUMO content localization starts
24
Planned 149.0.x
25
150 b8 GTB
150 QA sign off
26
27
150 b9 GTB
28
29
30
150 go to Build
31
RC

April 2026
SMTWTFS
1
2
151 soft Code Freeze starts at 08:00 UTC
3
String Freeze
151 regression testing completed
152 QA request deadline
4
5
6
Merge day
151 b1 GTB
Nightly 152 starts
7
150 Release
8
151 b2 GTB
9
10
151 b3 GTB
SUMO deadline
152 a11y engineering request deadline for Nightly
11
12
13
151 b4 GTB
14
Potential mobile 150.0.x
15
151 b5 GTB
16
17
151 b6 GTB
152 build ready for QA
Final deadline for QA’s Feature Test Plan approval
18
19
20
151 b7 GTB
SUMO content localization starts
21
Planned 150.0.x
22
151 b8 GTB
151 QA sign off
23
24
151 b9 GTB
25
26
27
151 go to Build
28
RC
29
30
152 soft Code Freeze starts at 08:00 UTC

May 2026
SMTWTFS
1
String Freeze
152 regression testing completed
153 QA request deadline
2
3
4
Merge day
152 b1 GTB
Nightly 153 starts
5
151 Release
6
152 b2 GTB
7
8
152 b3 GTB
SUMO deadline
153 a11y engineering request deadline for Nightly
9
10
11
152 b4 GTB
12
Potential mobile 151.0.x
13
152 b5 GTB
14
15
152 b6 GTB
153 build ready for QA
Final deadline for QA’s Feature Test Plan approval
16
17
18
152 b7 GTB
SUMO content localization starts
19
Planned 151.0.x
20
152 b8 GTB
152 QA sign off
21
22
152 b9 GTB
23
24
25
152 go to Build
26
RC
27
28
153 soft Code Freeze starts at 08:00 UTC
29
String Freeze
153 regression testing completed
154 QA request deadline
30
31

June 2026
SMTWTFS
1
Merge day
153 b1 GTB
Nightly 154 starts
2
152 Release
3
153 b2 GTB
4
5
153 b3 GTB
SUMO deadline
154 a11y engineering request deadline for Nightly
6
7
8
153 b4 GTB
9
Potential mobile 152.0.x
10
153 b5 GTB
11
12
153 b6 GTB
154 build ready for QA
Final deadline for QA’s Feature Test Plan approval
13
14
15
153 b7 GTB
SUMO content localization starts
16
Planned 152.0.x
17
153 b8 GTB
153 QA sign off
18
19
153 b9 GTB
20
21
22
153 go to Build
23
RC
24
25
154 soft Code Freeze starts at 08:00 UTC
26
String Freeze
154 regression testing completed
155 QA request deadline
27
28
29
Merge day
154 b1 GTB
Nightly 155 starts
30
153 Release

July 2026
SMTWTFS
1
154 b2 GTB
2
3
154 b3 GTB
SUMO deadline
155 a11y engineering request deadline for Nightly
4
5
6
154 b4 GTB
7
Potential mobile 153.0.x
8
154 b5 GTB
9
10
154 b6 GTB
155 build ready for QA
Final deadline for QA’s Feature Test Plan approval
11
12
13
154 b7 GTB
SUMO content localization starts
14
Planned 153.0.x
15
154 b8 GTB
154 QA sign off
16
17
154 b9 GTB
18
19
20
154 go to Build
21
RC
22
23
155 soft Code Freeze starts at 08:00 UTC
24
String Freeze
155 regression testing completed
156 QA request deadline
25
26
27
Merge day
155 b1 GTB
Nightly 156 starts
28
154 Release
29
155 b2 GTB
30
31
155 b3 GTB
SUMO deadline
156 a11y engineering request deadline for Nightly

August 2026
SMTWTFS
1
2
3
155 b4 GTB
4
Potential mobile 154.0.x
5
155 b5 GTB
6
7
155 b6 GTB
156 build ready for QA
Final deadline for QA’s Feature Test Plan approval
8
9
10
155 b7 GTB
SUMO content localization starts
11
Planned 154.0.x
12
155 b8 GTB
155 QA sign off
13
14
155 b9 GTB
15
16
17
155 go to Build
18
RC
19
20
156 soft Code Freeze starts at 08:00 UTC
21
String Freeze
156 regression testing completed
157 QA request deadline
22
23
24
Merge day
156 b1 GTB
Nightly 157 starts
25
155 Release
26
156 b2 GTB
27
28
156 b3 GTB
SUMO deadline
157 a11y engineering request deadline for Nightly
29
30
31
156 b4 GTB

September 2026
SMTWTFS
1
Potential mobile 155.0.x
2
156 b5 GTB
3
4
156 b6 GTB
157 build ready for QA
Final deadline for QA’s Feature Test Plan approval
5
6
7
156 b7 GTB
SUMO content localization starts
8
Planned 155.0.x
9
156 b8 GTB
156 QA sign off
10
11
156 b9 GTB
12
13
14
156 go to Build
15
RC
16
17
157 soft Code Freeze starts at 08:00 UTC
18
String Freeze
157 regression testing completed
158 QA request deadline
19
20
21
Merge day
157 b1 GTB
Nightly 158 starts
22
156 Release
23
157 b2 GTB
24
25
157 b3 GTB
SUMO deadline
158 a11y engineering request deadline for Nightly
26
27
28
157 b4 GTB
29
Potential mobile 156.0.x
30
157 b5 GTB

October 2026
SMTWTFS
1
2
157 b6 GTB
158 build ready for QA
Final deadline for QA’s Feature Test Plan approval
3
4
5
157 b7 GTB
SUMO content localization starts
6
Planned 156.0.x
7
157 b8 GTB
157 QA sign off
8
9
157 b9 GTB
10
11
12
157 go to Build
13
RC
14
15
158 soft Code Freeze starts at 08:00 UTC
16
String Freeze
158 regression testing completed
159 QA request deadline
17
18
19
Merge day
158 b1 GTB
Nightly 159 starts
20
157 Release
21
158 b2 GTB
22
23
158 b3 GTB
SUMO deadline
159 a11y engineering request deadline for Nightly
24
25
26
158 b4 GTB
27
Potential mobile 157.0.x
28
158 b5 GTB
29
30
158 b6 GTB
159 build ready for QA
Final deadline for QA’s Feature Test Plan approval
31

November 2026
SMTWTFS
1
2
158 b7 GTB
SUMO content localization starts
3
Planned 157.0.x
4
158 b8 GTB
158 QA sign off
5
6
158 b9 GTB
7
8
9
158 go to Build
10
RC
11
12
159 soft Code Freeze starts at 08:00 UTC
13
String Freeze
159 regression testing completed
160 QA request deadline
14
15
16
Merge day
159 b1 GTB
Nightly 160 starts
17
158 Release
18
159 b2 GTB
19
20
159 b3 GTB
SUMO deadline
160 a11y engineering request deadline for Nightly
21
22
23
159 b4 GTB
24
Potential mobile 158.0.x
25
159 b5 GTB
26
27
159 b6 GTB
160 build ready for QA
Final deadline for QA’s Feature Test Plan approval
28
29
30
159 b7 GTB
SUMO content localization starts

December 2026
SMTWTFS
1
2
Planned 158.0.x
159 b8 GTB
159 QA sign off
3
4
159 b9 GTB
5
6
7
159 go to Build
8
RC
9
10
160 soft Code Freeze starts at 08:00 UTC
11
String Freeze
160 regression testing completed
12
13
14
Merge day
160 b1 GTB
15
159 Release
16
160 b2 GTB
17
18
160 b3 GTB
SUMO deadline
19
20
21
160 b4 GTB
22
Potential mobile 159.0.x
23
160 b5 GTB
24
25
26
27
28
160 b6 GTB
29
Planned 159.0.x
30
160 b7 GTB
31

January 2027
SMTWTFS
1
2
3
4
160 b8 GTB
SUMO content localization starts
5
6
160 QA sign off
160 b9 GTB
7
8
9
10
11
160 go to Build
12
RC
13
14
15
16
17
18
19
160 Release
20
21
22
23
24
25
26
Potential mobile 160.0.x
27
28
29
30
31