diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 75bc448..16e814f 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -54,7 +54,30 @@ jobs:
         run: python -m pip install -e ".[dev]"
 
       - name: Run tests
-        run: python -m pytest tests/ -v
+        run: python -m pytest tests/ -v --cov --cov-report=term --cov-report=json
+
+      # Coverage badge: the percentage is written to a gist that shields.io
+      # renders in README. Only from main and from a single matrix entry so
+      # PRs and duplicate uploads never overwrite the number.
+      - name: Read coverage percentage
+        if: github.ref == 'refs/heads/main' && matrix.python-version == '3.12'
+        id: coverage
+        run: |
+          percent=$(python -c 'import json; print(round(json.load(open("coverage.json"))["totals"]["percent_covered"]))')
+          echo "percent=$percent" >> "$GITHUB_OUTPUT"
+
+      - name: Update coverage badge
+        if: github.ref == 'refs/heads/main' && matrix.python-version == '3.12'
+        uses: schneegans/dynamic-badges-action@v1.9.0
+        with:
+          auth: ${{ secrets.GIST_SECRET }}
+          gistID: 77b084ed0d46c740183f89ec66af8a95
+          filename: python-sdk-coverage.json
+          label: coverage
+          message: ${{ steps.coverage.outputs.percent }}%
+          valColorRange: ${{ steps.coverage.outputs.percent }}
+          minColorRange: 50
+          maxColorRange: 90
 
       - name: Verify package builds
         run: |
diff --git a/.gitignore b/.gitignore
index 16ded3f..8cef4a6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,6 +24,8 @@ ENV/
 # Testing
 .pytest_cache/
 .coverage
+coverage.json
+coverage.xml
 htmlcov/
 
 # Type checkers
diff --git a/pyproject.toml b/pyproject.toml
index cc3bfd3..cb344f3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -48,6 +48,7 @@ dev = [
     "ruff>=0.6",
     "mypy>=1.10",
     "types-requests>=2.28",
+    "pytest-cov>=4",
 ]
 
 [project.urls]
@@ -67,6 +68,13 @@ captcha_solver_api = ["py.typed"]
 [tool.pytest.ini_options]
 asyncio_mode = "auto"
 
+[tool.coverage.run]
+source = ["captcha_solver_api"]
+branch = true
+
+[tool.coverage.report]
+show_missing = true
+
 [tool.mypy]
 # mypy 2.x cannot target 3.9; 3.10 is the lowest it accepts. Runtime
 # compatibility with 3.9 is still covered by the CI test matrix.