Submitting custom pings

Custom pings can be submitted from JavaScript using:

TelemetryController.submitExternalPing(type, payload, options)
  • type - a string that is the type of the ping, limited to /^[a-z0-9][a-z0-9-]+[a-z0-9]$/i.

  • payload - the actual payload data for the ping, has to be a JSON style object.

  • options - optional, an object containing additional options:
    • addClientId- whether to add the client id to the ping, defaults to false

    • addEnvironment - whether to add the environment data to the ping, defaults to false

    • overrideEnvironment - a JSON style object that overrides the environment data

TelemetryController will assemble a ping with the passed payload and the specified options. That ping will be archived locally for use with Shield and inspection in about:telemetry. If preferences allow the upload of Telemetry pings, the ping will be uploaded at the next opportunity (this is subject to throttling, retry-on-failure, etc.).


Every new or changed data collection in Firefox needs a data collection review from a Data Steward.

Submission constraints

When submitting pings on shutdown, they should not be submitted after Telemetry shutdown. Pings should be submitted at the latest within:

There are other constraints that can lead to a ping submission getting dropped:

  • invalid ping type strings.

  • invalid payload types: E.g. strings instead of objects.

  • oversized payloads: We currently only drop pings >1MB, but targeting sizes of <=10KB is recommended.


Helpful tools for designing new pings include:

  • gzipServer - a Python script that can run locally and receives and saves Telemetry pings. Making Firefox send to it allows inspecting outgoing pings easily.

  • about:telemetry - allows inspecting submitted pings from the local archive, including all custom ones.

Designing custom pings

In general, creating a new custom ping means you don’t benefit automatically from the existing tooling. Further work is needed to make data show up in re:dash or other analysis tools.

In addition to the data collection review, questions to guide a new ping design are:

  • Submission interval & triggers:
    • What events trigger ping submission?

    • What interval is the ping submitted in?

    • Is there a throttling mechanism?

    • What is the desired latency? (submitting “at least daily” still leads to certain latency tails)

    • Are pings submitted on a clock schedule? Or based on “time since session start”, “time since last ping” etc.? (I.e. will we get sharp spikes in submission volume?)

  • Size and volume:
    • What’s the size of the submitted payload?

    • What’s the full ping size including metadata in the pipeline?

    • What’s the target population?

    • What’s the overall estimated volume?

  • Dataset:
    • Is it opt-out?

    • Does it need to be opt-out?

    • Does it need to be in a separate ping? (why can’t the data live in probes?)

  • Privacy:
    • Is there risk to leak PII?

    • How is that risk mitigated?

  • Data contents:
    • Does the submitted data answer the posed product questions?

    • Does the shape of the data allow to answer the questions efficiently?

    • Is the data limited to what’s needed to answer the questions?

    • Does the data use common formats? (i.e. can we reuse tooling or analysis know-how)