diff --git a/.github/scripts/coverage-badge.py b/.github/scripts/coverage-badge.py
new file mode 100644
index 0000000..9334e18
--- /dev/null
+++ b/.github/scripts/coverage-badge.py
@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+"""Reads a Cobertura report, writes a coverage badge (SVG) and a Markdown summary."""
+import sys
+import xml.etree.ElementTree as ET
+
+report, badge, summary = sys.argv[1:4]
+root = ET.parse(report).getroot()
+line = float(root.attrib["line-rate"]) * 100
+branch = float(root.attrib["branch-rate"]) * 100
+
+color = "#4c1" if line >= 90 else "#dfb317" if line >= 75 else "#e05d44"
+label, value = "coverage", f"{line:.0f}%"
+lw, vw = 61, 6 * len(value) + 14
+w = lw + vw
+
+with open(badge, "w") as f:
+    f.write(f"""<svg xmlns="http://www.w3.org/2000/svg" width="{w}" height="20" role="img" aria-label="{label}: {value}">
+<linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient>
+<clipPath id="r"><rect width="{w}" height="20" rx="3" fill="#fff"/></clipPath>
+<g clip-path="url(#r)"><rect width="{lw}" height="20" fill="#555"/><rect x="{lw}" width="{vw}" height="20" fill="{color}"/><rect width="{w}" height="20" fill="url(#s)"/></g>
+<g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" font-size="11">
+<text x="{lw / 2}" y="15" fill="#010101" fill-opacity=".3">{label}</text><text x="{lw / 2}" y="14">{label}</text>
+<text x="{lw + vw / 2}" y="15" fill="#010101" fill-opacity=".3">{value}</text><text x="{lw + vw / 2}" y="14">{value}</text>
+</g></svg>
+""")
+
+rows = "\n".join(
+    f"| {c.attrib['name']} | {float(c.attrib['line-rate']) * 100:.0f}% |"
+    for c in sorted(root.iter("class"), key=lambda c: c.attrib["name"])
+    if "/" not in c.attrib["name"] and "<" not in c.attrib["name"]
+)
+with open(summary, "w") as f:
+    f.write(f"## Code coverage\n\nLines: **{line:.1f}%** · Branches: **{branch:.1f}%**\n\n| Class | Lines |\n|---|---|\n{rows}\n")
diff --git a/.github/workflows/dotnet.yml b/.github/workflows/dotnet.yml
index aaa5c26..60ce4d9 100644
--- a/.github/workflows/dotnet.yml
+++ b/.github/workflows/dotnet.yml
@@ -12,6 +12,8 @@ jobs:
       matrix:
         os: [ ubuntu-latest, windows-latest, macos-latest ]
     runs-on: ${{ matrix.os }}
+    permissions:
+      contents: write
     steps:
     - uses: actions/checkout@v7
       with:
@@ -25,4 +27,20 @@ jobs:
     - name: Build
       run: dotnet build -c Release --no-restore
     - name: Test
-      run: dotnet test -c Release --no-build --verbosity normal
+      run: dotnet test -c Release --no-build --verbosity normal --collect:"XPlat Code Coverage" --results-directory ./coverage
+    - name: Coverage summary and badge
+      if: matrix.os == 'ubuntu-latest'
+      run: |
+        python3 .github/scripts/coverage-badge.py "$(ls coverage/*/coverage.cobertura.xml | head -n1)" coverage/coverage.svg "$GITHUB_STEP_SUMMARY"
+    - name: Publish coverage badge
+      if: matrix.os == 'ubuntu-latest' && github.event_name == 'push'
+      env:
+        GITHUB_TOKEN: ${{ github.token }}
+      run: |
+        cd coverage
+        git init -q -b badges
+        git config user.name "github-actions[bot]"
+        git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+        git add coverage.svg
+        git commit -q -m "Update coverage badge"
+        git push -f "https://x-access-token:${GITHUB_TOKEN}@github.com/${{ github.repository }}.git" badges
diff --git a/.gitignore b/.gitignore
index 48533d5..1a10596 100644
--- a/.gitignore
+++ b/.gitignore
@@ -756,4 +756,7 @@ FodyWeavers.xsd
 ### VisualStudio Patch ###
 # Additional files built by Visual Studio
 
-# End of https://www.toptal.com/developers/gitignore/api/dotnetcore,linux,windows,macos,jetbrains,rider,visualstudio,visualstudiocode,aspnetcore
\ No newline at end of file
+# End of https://www.toptal.com/developers/gitignore/api/dotnetcore,linux,windows,macos,jetbrains,rider,visualstudio,visualstudiocode,aspnetcore
+
+# Local coverage output
+/coverage/
diff --git a/README.md b/README.md
index 6c970a2..af37237 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,5 @@
 [![.NET](https://github.com/capjan/regex/actions/workflows/dotnet.yml/badge.svg)](https://github.com/capjan/regex/actions/workflows/dotnet.yml)
+[![Coverage](https://raw.githubusercontent.com/capjan/regex/badges/coverage.svg)](https://github.com/capjan/regex/actions/workflows/dotnet.yml)
 
 # regex