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Set Environment Variables

Configure your environment variables to allow Percy builds to run seamlessly

Percy integrates with your tests using both Percy and BrowserStackSDK. To establish this integration, choose the appropriate SDK and refer to the following section accordingly:

To seamlessly integrate your visual and functional testing processes for your website, execute your Percy tests on BrowserStack’s Automate. If you’re already an Automate user and wish to explore Percy, you can do so as well. Leveraging BrowserStack SDK for running your tests fulfills all requirements.

Supported parameters

Percy client libraries retrieve additional details from the environment they are running in, including the branch name, commit SHA, GitHub Pull Request number, and more. You can modify certain aspects of Percy’s behavior by configuring these environment variables within your CI environment:

Environment Variable Description
PERCY_BRANCH The branch in which the build is being executed. Default is the current git branch.
PERCY_PULL_REQUEST The pull request number to link with the build, if any.
PERCY_PARALLEL_TOTAL The total number of parallel builds to expect. \n- In most setups this is automatically discovered and does not need to be set. To know more, read Parallel test suites.
PERCY_PARALLEL_NONCE A unique identifier used to group parallel builds. This can be any string that is shared between parallel runners, such as the CI build number. \n - In most setups this is automatically discovered and does not need to be set. To know more, read Parallel test suites.
PERCY_PARTIAL_BUILD Set to 1 to indicate the build is a partial build, and that it intentionally will be a subset of the snapshots from a full build.
HTTP_PROXY Set http proxy that Percy cli should use in case you need to access internet over a corporate proxy.
HTTPS_PROXY Set https proxy that Percy cli should use in case if you need to access internet over a corporate proxy

In most cases setting only HTTP_PROXY should suffice, but if you have separate proxies for HTTP and HTTPS feel free to set both.

The format for proxy’s is http[s]://<username>:<password>@<domain.com>:<port>/ [username and password is optional].
PERCY_COMMIT Set this to the Git commit SHA to ensure that visual tests and snapshots taken by Percy are correctly linked to a specific commit in the version control system.
PERCY_GZIP Set this to true to potentially optimize resource size within the 25 MB threshold limit. The default is set to false.

Percy is designed to integrate with your tests locally and with your CI environment. To establish this integration, set the PERCY_TOKEN environment variable by following these steps:

IMPORTANT

  • Keep your Percy token secret. Anyone with access to your token can consume your account quota.
  • The “write-only” token can only be used to make changes, not to view your data.

Get PERCY_TOKEN

A Percy token is generated when you create a Percy project. The token is a write-only API key that is unique for each project. You can find this on the Project Settings page.Percy Token

You can set a project-specific token with three access levels:

  • Read-only: With this, you can retrieve project information using the GET API call.
  • Write-only: This serves as a project-specific API key, allowing you to create builds, snapshots, and upload resources to the project.
  • Full-access: This serves as a project-specific read/write API key, allowing you to read build information, download snapshots, create builds and snapshots, and upload resources to the project.

Learn more about which feature works with which access levels.

Set PERCY_TOKEN as environment variable
You can run Percy:

To learn about how to set your Percy token as an environment variable, see the relevant section.

Note

  • Percy works best when triggered automatically from your CI environment, but can also be run from your local development environment. This is helpful during the initial integration of Percy.
  • As of CLI version 1.26.7, the default configuration for all users involves automatically sending terminal logs to Percy to enhance support and improve services. However, we value your privacy and offer an option to opt out of this feature using an environment variable. You can use the following command to opt out: export PERCY_CLIENT_ERROR_LOGS=false

Run Percy locally

To run Percy locally, set the PERCY_TOKEN environment variable using the export keyword as shown:

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Alternatively, you can set the PERCY_TOKEN environment variable locally in a single line. For example:

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Now you can run your tests locally.

Note

  • When running in your local environment, it is recommended to set the PERCY_BRANCH environment variable to “local” to prevent unintentionally overwriting of your project’s master baseline in Percy. While not compulsory, this measure ensures the preservation of any baselines established by CI.
  • If you don’t use the PERCY_BRANCH variable while you run local tests and you happen to be on the master branch, then it will result in setting the baseline for your project in Percy as the master branch.

Run from your CI setup

To run Percy from your CI workflow, update both the CI configuration file and the pipeline script. Learn more.

Percy works best when integrated into your CI workflow, running continuously alongside your test suite. It seamlessly integrates with major CI providers and offers configurability for custom environments.

Note
We recommend to run Percy via your CI workflow.

Supported parameters

Percy client libraries retrieve additional details from the environment they are running in, including the branch name, commit SHA, GitHub Pull Request number, and more. You can modify certain aspects of Percy’s behavior by configuring these environment variables within your CI environment:

Environment Variable Description
PERCY_TOKEN A Percy token is a project-specific, write-only API key.
PERCY_BRANCH The branch in which the build is being executed. Default is the current git branch.
PERCY_TARGET_BRANCH The branch for comparison. Default set to master. \n- If the Percy build is associated to a GitHub Pull Request, setting this value will have no effect and the target branch will be automatically determined from the GitHub PR. To know more, read base build docs.
PERCY_TARGET_COMMIT The full commit SHA of an existing Percy build to be used as the reference baseline. To know more, read base build docs.
PERCY_PULL_REQUEST The pull request number to link with the build, if any.
PERCY_PARALLEL_TOTAL The total number of parallel builds to expect. \n- In most setups this is automatically discovered and does not need to be set. To know more, read Parallel test suites.
PERCY_PARALLEL_NONCE A unique identifier used to group parallel builds. This can be any string that is shared between parallel runners, such as the CI build number. \n - In most setups this is automatically discovered and does not need to be set. To know more, read Parallel test suites.
PERCY_PARTIAL_BUILD Set to 1 to indicate the build is a partial build, and that it intentionally will be a subset of the snapshots from a full build.
PERCY_ENABLE Set to 0 to prevent Percy running in your CI environment. This can be useful to set conditionally if you want Percy to be disabled in certain scenarios.
PERCY_DEBUG Set to true to debug asset discovery and do not upload snapshots.
PERCY_LOGLEVEL Set it to any of the following: ‘info’, ‘silent’, ‘warn’ or ‘debug’.
HTTP_PROXY Set http proxy that Percy cli should use in case you need to access internet over a corporate proxy.
HTTPS_PROXY Set https proxy that Percy cli should use in case if you need to access internet over a corporate proxy

In most cases setting only HTTP_PROXY should suffice, but if you have separate proxies for HTTP and HTTPS feel free to set both.

The format for proxy’s is http[s]://<username>:<password>@<domain.com>:<port>/ [username and password is optional].
PERCY_NETWORK_IDLE_WAIT_TIMEOUT This is maximum amount of time Percy cli’s resource discovery browser would wait for networkIdleTimeout to hit. This is defaulted to 30000ms [ 30 sec ].
PERCY_PAGE_LOAD_TIMEOUT This is maximum amount of time Percy cli’s resource discovery browser would wait for page to load. This is defaulted to 30000ms [ 30 sec ].
PERCY_SKIP_UPDATE_CHECK Set to true to skip CLI update checks we queryapi.github.com for newer CLI releases tags, if this env is not set false.
PERCY_CLIENT_ERROR_LOGS Set to false to prevent the test script from sending logs to Percy.
PERCY_COMMIT Set this to the Git commit SHA to ensure that visual tests and snapshots taken by Percy are correctly linked to a specific commit in the version control system.
PERCY_DO_NOT_CAPTURE_RESPONSIVE_ASSETS Set this to true, and it will not capture responsive assets like images for that page. The default is set to false.
PERCY_EXIT_WITH_ZERO_ON_ERROR Set this to true, and this will exit with code 0 for any Percy-related errors, and the error logs will be available. The default is set to false.
PERCY_GZIP Set this to true to potentially optimize resource size within the 25 MB threshold limit. The default is set to false.

Note
With the latest version of @percy/cli, any of the environment variables defined on this page can be specified within a .env file in current working directory.

PERCY_TOKEN access levels

Components of Feature Read Write Full
Synchronous Comparison Results No No Yes
Percy Screenshot No Yes Yes
Percy Snapshot No Yes Yes
Upload screenshots No Yes Yes
CI Integration No Yes Yes
API Reference - GET Yes No Yes
API Reference - PUT/POST No Yes Yes
  • Every feature that uses the Percy Screenshot and Percy Snapshot commands will have the same access, except for Synchronous CLI.
  • We recommend using the ‘Write’ access mode for CI integration.

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