== Engineering ==
Experiments are a special type of [https://developer.mozilla.org/en-US/Add-ons/Bootstrapped_extensions restartless extension]. They can do anything a regular restartless extension can do. Detailed instructions on the mechanics of developing and testing the experiment can be found at [[QA/Telemetry/Developing_a_Telemetry_Experiment|Developing a Telemetry Experiment]].
=== Repository and Reviews === Experiments must be developed in the public [http://hg.mozilla.org/webtools/telemetry-experiment-server telemetry experiment server] source repository and must be reviewed just as if they were part of Firefox on mozilla-central. If an experiment adds special data collection, that data collection must be [[Firefox/Data Collection|documented and reviewed]] as normal. There are more detailed instructions on the mechanics of developing and testing the experiment at [[QA/Telemetry/Developing_a_Telemetry_Experiment|Developing a Telemetry Experiment]]. To request reviews, file a bug against the [https://bugzilla.mozilla.org/enter_bug.cgi?product=Firefox%20Health%20Report&component=Client%3A%20Desktop Firefox Health Report product, Desktop Client component]. === <code>install.rdf</code> === Experiments, like other restartless extensions, should have an <code>install.rdf</code> manifest file. However, unlike other extensions, the [https://developer.mozilla.org/en-US/Add-ons/Install_Manifests#type type] must be set to 128. === <code>manifest.json</code> === Unlike other restartless extensions, experiments must have a top-level <code>manifest.json</code> file. The <code>manifest.json</code> format is not currently documented, though examples can be found by looking at past experiments [http://hg.mozilla.org/webtools/telemetry-experiment-server in the telemetry-experiment-server mercurial repo]. In particular, note that the <code>name</code> field is visible to end users, so it should be accurate and not confusing. === Extension Lifecycle ===
Most experiments live for a fixed period and are uninstalled by the experiment system at the end date or after the specified elapsed time.
A few experiments are intended to collect data once and then uninstall themself. These experiments should uninstall themselves when done by calling <code>Experiments.disableExperiment("FROM_API")</code>.
=== Extension Signing ===
Telemetry Experiments need to be signed to run in FF 42+, just like all other add-ons.
