# Field trials WebRTC provides some means to alter its default behavior during run-time, colloquially known as *field trials*. This is foremost used for A/B testing new features and are related to [Chromium field trials](https://chromium.googlesource.com/chromium/src/+/main/testing/variations/README.md) to facilitate interoperability. A field trial consist of a key-value pair of strings. By convention, the field trial key is prefixed with `WebRTC-` and each word is capitalized without spaces. Sometimes the key is further subdivided into a category, for example, `WebRTC-MyCategory-MyExperiment`. The field trial value is an opaque string and it is up to the author to define what it represents. There are [helper functions](https://webrtc.googlesource.com/src/+/refs/heads/main/api/field_trials_view.h) to use a field trial as a boolean, with the string `Enabled` representing true and `Disabled` representing false. You can also use [field trial parameters](https://webrtc.googlesource.com/src/+/refs/heads/main/rtc_base/experiments/field_trial_parser.h) if you wish to encode more elaborate data types. The set of field trials can be instantiated from a single string with the format `////`. Note the final `/` at the end! In Chromium you can launch with the `--force-fieldtrials` flag to instantiate field trials this way, for example: ``` --force-fieldtrials="WebRTC-Foo/Enabled/WebRTC-Bar/Disabled/" ``` ## Policy The policy for field trials is: - A field trial should only be used to test out new code or parameters for a limited time period. It should not be used for configuring persistent behavior. - The field trial must have an end date. The end date may be pushed back if necessary, but should not be pushed back indefinitely. - A field trial must be associated with a bug that - reserves the field trial key, - is open, - is assigned to an owner, and - has the end date specified.