Stopping GLAM processing of Legacy Telemetry data in January
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Chris H-C
Dec 2, 2025, 3:04:55 PMDec 2
to Data Announcements, fx-da...@mozilla.org, data-org
Hello!
As part of the Instrumentation Consolidation Project (aka FOG Migration) whereby we're aligning Firefox Desktop with the rest of Mozilla's projects in their use of Glean for data collection, we're progressively shuttering the processing of Legacy-Telemetry-sent data in favour of its Glean-sent equivalents when possible.
We have identified Legacy Telemetry data in GLAM ( https://glam.telemetry.mozilla.org/ our public, one-click data exploration tool ) as the next we can deprecate in this way as, not only has the final Legacy Telemetry probe been mirrored-to by Glean metrics since July (most for much longer[1]), GLAM's processing is computationally (and financially) expensive.
Starting in January of 2026 (exact date to be determined, but definitely after the end-of-year deployment freeze), GLAM will stop processing incoming Legacy Telemetry data (which will continue to be collected and derived into non-GLAM datasets as normal). We will post a warning on every page displaying Legacy-Telemetry-sent data that it will no longer update. These pages and the data processed up to that point will remain available until at least June 30, 2026, after which point we intend to erase the data and remove Legacy Telemetry pages from GLAM's frontend.
Glean-sent data will continue to be available on GLAM as normal and we expect it to serve all analysis purposes that the Legacy-Telemetry-sent data did. The raw Legacy-Telemetry-sent data that would have been processed for display on GLAM will still be available as normal, should it be required.
Legacy Telemetry data is viewed infrequently on GLAM (we see a few dozen API hits most days), so we don't expect this to be too disruptive. If you'd like to comment or have a question, please feel free to reply to this email or seek us out on the #glean channel on Slack or Matrix.
In summary: Legacy Telemetry data on GLAM will be frozen at the beginning of 2026, to be removed from GLAM after June. Use Glean equivalents instead. Reply to this email, or message Slack#glean or #glean:mozilla.org if you have questions.
Chris H-C (:chutten)
On behalf of the Instrumentation Consolidation Project (FOG Migration)
[1]: https://arewegleanyet.com/
As part of the Instrumentation Consolidation Project (aka FOG Migration) whereby we're aligning Firefox Desktop with the rest of Mozilla's projects in their use of Glean for data collection, we're progressively shuttering the processing of Legacy-Telemetry-sent data in favour of its Glean-sent equivalents when possible.
We have identified Legacy Telemetry data in GLAM ( https://glam.telemetry.mozilla.org/ our public, one-click data exploration tool ) as the next we can deprecate in this way as, not only has the final Legacy Telemetry probe been mirrored-to by Glean metrics since July (most for much longer[1]), GLAM's processing is computationally (and financially) expensive.
Starting in January of 2026 (exact date to be determined, but definitely after the end-of-year deployment freeze), GLAM will stop processing incoming Legacy Telemetry data (which will continue to be collected and derived into non-GLAM datasets as normal). We will post a warning on every page displaying Legacy-Telemetry-sent data that it will no longer update. These pages and the data processed up to that point will remain available until at least June 30, 2026, after which point we intend to erase the data and remove Legacy Telemetry pages from GLAM's frontend.
Glean-sent data will continue to be available on GLAM as normal and we expect it to serve all analysis purposes that the Legacy-Telemetry-sent data did. The raw Legacy-Telemetry-sent data that would have been processed for display on GLAM will still be available as normal, should it be required.
Legacy Telemetry data is viewed infrequently on GLAM (we see a few dozen API hits most days), so we don't expect this to be too disruptive. If you'd like to comment or have a question, please feel free to reply to this email or seek us out on the #glean channel on Slack or Matrix.
In summary: Legacy Telemetry data on GLAM will be frozen at the beginning of 2026, to be removed from GLAM after June. Use Glean equivalents instead. Reply to this email, or message Slack#glean or #glean:mozilla.org if you have questions.
Chris H-C (:chutten)
On behalf of the Instrumentation Consolidation Project (FOG Migration)
[1]: https://arewegleanyet.com/
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