Coverage.py is a free tool for measuring which parts of a Python program run and which executable code is missed. It helps people assess how thoroughly tests exercise a program. Statement coverage is measured by default, with branch coverage also available. Reports can be produced as text, HTML, XML, LCOV, or JSON, and dynamic contexts can associate executed lines with the test function that ran them. Test suites can run through their usual command; pytest-cov is also available, though the documentation says most users do not need it. Third-party plugins can extend measurement to non-Python files, such as connecting executed Python to Django templates. Coverage data is stored in SQLite, and advanced users can work with the Coverage.py API. The documented interpreters include Python 3.10 through 3.15 rc2 and PyPy3 3.10 and 3.11. It offers ctrace and pytrace cores, plus sysmon, which is faster for simple line and branch coverage but lacks support for dynamic contexts and plugins. Coverage.py is licensed under Apache 2.0 and supports Linux, macOS, Windows, and self-hosting.

Who it is for

Coverage.py suits Python developers who want to see which code their tests cover and where they leave gaps. It also fits teams that need multiple report formats or coverage data tied to individual test functions.

What is good

Free plan and Apache 2.0 license
Measures statement and branch coverage
Produces five report formats
Dynamic contexts link lines to test functions
Plugins can extend measurement beyond Python

What to know first

sysmon does not support dynamic contexts
sysmon does not support plugins

Verdict

Coverage.py provides several ways to measure and report Python test coverage, including optional branch coverage and test-specific contexts. Its sysmon core has narrower capabilities, so users needing contexts or plugins should note that limitation.

Coverage.py plans and pricing

All plans

Coverage.py Free Open-source Python coverage tool · Enterprise subscription available through Tidelift coverage.readthedocs.io · 3 Oct 2026

Compared on test coverage tools

Free plan: Yes
Coverage types: statement, branch
Supported languages: Python
Report formats: text, HTML, XML, LCOV, JSON
Self-hosted option: Yes
Coverage gates: Yes

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The record

Purpose

Coverage.py measures which parts of Python programs ran and identifies executable code that did not run, commonly to gauge test effectiveness.

Reports

It can produce text, HTML, XML, LCOV, and JSON reports.

Contexts

Dynamic contexts can record which test function ran which lines of code.

Integrations

Coverage.py can run test suites through their usual command, and pytest-cov is an available pytest plugin that the docs say is unnecessary for most purposes.

Extensibility

Third-party plugins can extend measurement to non-Python files, such as mapping executed Python back to Django HTML templates.

Storage and API

Coverage data is stored in a SQLite database, and advanced usage can use the Coverage.py API.

Supported interpreters

The current documentation lists Python 3.10 through 3.15 rc2, including free-threading, and PyPy3 versions 3.10 and 3.11.

Measurement cores

Coverage.py offers ctrace and pytrace tracing cores plus a sysmon core; sysmon is faster for simple line and branch coverage but does not yet support dynamic contexts or plugins.

Security

The project directs vulnerability reports to Tidelift, which it says will coordinate the fix and disclosure.

License

Coverage.py is licensed under the Apache 2.0 License.

Support

Users can seek help on the Python discussion forums or Python Discord, report bugs on GitHub, and obtain professional support through Tidelift Subscription.

Intended users

The documentation presents Coverage.py as a tool for people measuring Python test effectiveness by seeing which code tests exercise and which they miss.

Price from

Free