# Accessibility Performance Measurements Accessibility support can have a negative impact on performance, so it is important to test for regressions and to improve performance over time. This can be done with Chromium's performance testing framework, [Telemetry](https://chromium.googlesource.com/catapult/+/HEAD/telemetry/README.md). The metrics for accessibility are defined in [third_party/catapult/tracing/tracing/metrics/accessibility_metric.html](https://cs.chromium.org/chromium/src/third_party/catapult/tracing/tracing/metrics/accessibility_metric.html). ## Stories A story is a url to load and actions to take on that page. Accessibility stories are defined in [tools/perf/page_sets/system_health/accessibility_stories.py](https://cs.chromium.org/chromium/src/tools/perf/page_sets/system_health/accessibility_stories.py). If a particular web page seems slow, you may add a new story here to track its performance. ### Running stories from the command line To run all accessibility stories locally using the currently installed Canary browser: ```shell tools/perf/run_benchmark system_health.common_desktop \ --story-filter="accessibility.*" \ --browser canary ``` To run the same set of tests on your own compiled version of Chrome: ```shell tools/perf/run_benchmark system_health.common_desktop \ --story-filter="accessibility.*" \ --browser=exact \ --browser-executable=out/Release/chrome ``` For more information, see the [Telemetry documentation](https://github.com/catapult-project/catapult/blob/main/telemetry/docs/run_benchmarks_locally.md) or command-line help for tools/perf/run_benchmark. ### Capture web page replay for new or modified stories You should capture web page replay information whenever you add or modify a story. To do so, see [here](../../../tools/perf/recording_benchmarks.md). ## Blink Perf Blink perf tests are microbenchmarks that track the performance of a small function or operation in isolation. You can find these tests in [third_party/blink/perf_tests/accessibility/](https://cs.chromium.org/chromium/src/third_party/blink/perf_tests/accessibility/). To run these tests locally on your own compiled Chrome: ```shell tools/perf/run_benchmark blink_perf.accessibility \ --browser=exact \ --browser-executable=out/Release/chrome ``` ## Results The results can be found at [https://chromeperf.appspot.com](chromeperf.appspot.com). ## Google-internal Info More information on analytics and performance, including some additional Google-internal resources, can be found at [go/chrome-a11y/resources/analytics-performance](http://go/chrome-a11y/resources/analytics-performance).