CODEOWNERS Coverage Analyzer

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CODEOWNERS file:

Use the base-branch CODEOWNERS content. Rules stay case-sensitive to match GitHub behavior.

Drop CODEOWNERS or TXT onto the textarea.

Changed files:

One changed path per line. Status prefixes such as M, A, D, R100, and tab-delimited rename rows are normalized.

Drop TXT, DIFF, PATCH, or CSV onto the textarea.

Review input

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CODEOWNERS coverage is a pull-request readiness check for repository ownership. It compares the files changed in a review with the ownership rules that should route those files to the right people or teams. A strong coverage pass makes it harder for sensitive paths, migration folders, infrastructure changes, and ownership-file edits to slip through with only a broad default reviewer.

The useful question is not only whether a path has any matching rule. It is whether the winning rule is specific enough for the risk of the change. A catch-all owner may be acceptable for a README edit, while the same default owner on infra/main.tf or db/migrations/20260501.sql may be too weak for a merge gate. CODEOWNERS review also depends on the base branch, so the ownership text used for a pull request should match the branch that will receive the merge.

Flow diagram showing CODEOWNERS rules and changed files matched into a winning rule, gate metrics, remediation queue, and owner group chart.

Coverage numbers are review signals, not proof that a repository is governed perfectly. A high percentage does not confirm that every listed user or team still exists, has write access, or is the best reviewer for the change. A low percentage usually points to missing ownership rules, ownerless exceptions, or broad fallback rules that need attention before the pull request is treated as ready.

The most useful review brief keeps three facts together: the changed path, the rule that won for that path, and the action needed if the rule is missing, ownerless, or too broad for a protected area. That makes the result actionable for maintainers instead of leaving them with a raw ownership file and a diff list to inspect by hand.

Technical Details:

CODEOWNERS matching is ordered text matching. Each usable rule starts with a path pattern and then lists one or more owners. Later matching rules take precedence over earlier matching rules, so a general fallback such as * @org/platform can be narrowed by a later /infra/ @org/platform-infra rule. Paths are matched case-sensitively, which matters when a developer workstation is less strict than the repository host.

Some ownership syntax differs from ordinary gitignore habits. Negation patterns beginning with ! and bracket character ranges such as [a-z] are not valid CODEOWNERS syntax. Empty owner lines can intentionally create ownerless exceptions for subdirectories, while invalid lines should be treated as skipped rather than silently trusted.

The coverage calculation counts changed files after optional ignore patterns are removed. A file contributes to owner-assigned coverage when the winning rule has at least one owner. It contributes to direct owner coverage only when that winning rule is not the catch-all * rule.

Owner-assigned coverage = \frac{changed files with an owner-assigned winning rule}{checked changed files} \times 100

A separate remediation count is stricter than the percentage. Missing owners, ownerless overrides, protected paths covered only by a catch-all rule, and an unprotected CODEOWNERS edit can all queue review work even when the overall percentage looks high.

Rule matching and coverage classification logic
Rule or path condition	Classification	Review meaning
No usable rule matches the changed path.	Missing owner	Add an ownership rule or route the pull request to explicit maintainers.
The winning rule has a pattern but no owners.	Ownerless override	Confirm the exception is intentional; protected paths should receive a specific owner.
The winning rule is `*` and the path is not protected.	Catch-all owner	Review with the default owner, then consider a narrower rule if the path recurs.
The winning rule is `*` and the path matches a protected prefix.	Baseline only	Add a scoped owner rule before treating the protected change as covered.
The winning rule has owners and is not the catch-all.	Covered	Request the listed owner or team and keep the matching line as evidence.

Changed-file input can come from a plain path list, short status output, or name-status diff output. Rename rows use the new path because the merge result is what needs an owner. Duplicate changed paths are counted once, and ignored paths are removed before the denominator is calculated.

Inputs and outputs that affect CODEOWNERS coverage analysis
Item	Accepted or reported form	Why it matters
`CODEOWNERS file`	Rules with comments, owners, ownerless overrides, and last-match precedence.	Provides the ownership rules checked against each changed path.
`Changed files`	One path per line, `git status --short`, `git diff --name-status`, simple CSV, or rename rows.	Defines the review surface and the coverage denominator.
`Protected path prefixes`	Comma- or newline-separated prefixes such as `.github/`, `infra/`, and `db/migrations/`.	Marks paths where a catch-all owner is treated as too broad.
`Coverage target`	0 to 100 percent.	Creates the pass/fail percentage used in Coverage Gate Metrics.
`Ignored path patterns`	Optional CODEOWNERS-style patterns for generated files, vendored trees, snapshots, or other excluded paths.	Removes known exclusions before coverage, charts, and remediation are built.

Everyday Use & Decision Guide:

Use the base-branch ownership text for the pull request under review, then paste the files from the same change set. A good first pass is a name-status list from Git, a coverage target near the team policy, and protected prefixes for ownership-sensitive areas such as .github/, infra/, and database migration folders.

Leave Require CODEOWNERS self-owner on when the changed files include .github/CODEOWNERS, CODEOWNERS, or docs/CODEOWNERS. Ownership rules can weaken themselves, so a CODEOWNERS edit should have a direct owner rule for the file or its directory instead of relying on the repository fallback.

Open Coverage Gate Metrics first to see the owner-assigned percentage, direct owner percentage, skipped rules, ignored files, and target shortfall.
Use Path Owner Ledger when reviewers need path-by-path evidence. It shows the changed path, path group, owner outcome, winning rule, and recommended action.
Work through Owner Remediation Queue before merge if it lists missing owners, ownerless overrides, protected catch-all matches, syntax skips, or a CODEOWNERS self-owner gap.
Check Owner Coverage by Group when a pull request touches several areas. The chart separates specific owners, catch-all owners, protected catch-all matches, and owner gaps by path group.

Use Ignored path patterns sparingly. Excluding generated files, vendor directories, or snapshots can make a review brief cleaner, but every exclusion changes the denominator. If the ignored-file count is nonzero, confirm that each excluded path is expected for this review.

A green-looking percentage does not prove that the listed owners can approve the pull request. Confirm team visibility, write access, and branch-protection behavior in the repository when the result will be used as merge evidence.

Step-by-Step Guide:

Follow one pull request at a time so the coverage percentage and remediation rows stay tied to one review decision.

Enter a short label in Repository. The label appears in the exported brief and JSON so copied evidence remains attached to the right repository.
Set Coverage target to the expected gate, such as 95%. Coverage Gate Metrics will show the actual percentage and any target shortfall.
Add comma- or newline-separated Protected path prefixes for directories that need specific ownership. A changed path under those prefixes will be flagged if it only matches *.
Paste or browse for the base-branch CODEOWNERS file. The status badge above the textarea should show active rules, ownerless overrides, and skipped rules.
Paste or browse for Changed files. Plain paths, short status rows, name-status rows, patch-style file lists, and CSV-like lists are normalized; rename rows keep the new path.
Open Owner Remediation Queue if the summary badge says owner work queued. Fix missing owners, ownerless overrides, protected catch-all matches, skipped syntax, or CODEOWNERS self-owner gaps before trusting the gate.

If the page shows Changed files are required or At least one usable CODEOWNERS rule is required, restore the missing textarea content before reading the coverage result.

Interpreting Results:

The summary percentage is owner-assigned coverage: changed files with any owner-bearing winning rule divided by checked changed files. The owner gate clear badge requires more than hitting the target. There must be at least one changed file, no remediation items, and no skipped CODEOWNERS syntax.

Direct owner coverage is often the stronger signal for risky changes because it excludes the catch-all rule. If owner-assigned coverage is high but direct owner coverage is low, the pull request may be relying heavily on a broad fallback owner.

Missing owner means no usable rule matched the changed path.
Ownerless override means a matching rule intentionally has no owner. Treat it as a review decision, not as covered ownership.
Baseline only means a protected path matched the catch-all rule. Add a more specific owner before using the result as merge evidence.
Skipped line means CODEOWNERS syntax was not accepted by the local parser, so the affected rule should be fixed or checked directly in the repository host.

Worked Examples:

Platform pull request with one ownerless exception. A review uses * @org/platform, direct rules for /.github/, /db/, /src/frontend/, and /infra/, plus an ownerless /apps/github exception. Seven changed files include .github/CODEOWNERS, infra/main.tf, README.md, and apps/github/experimental.js. Coverage Gate Metrics reports 85.7% owner-assigned coverage against a 95% target, and Owner Remediation Queue lists the ownerless override and coverage target shortfall. The README is still owned by the catch-all rule, but the ownerless app path keeps the gate from clearing.

Infrastructure change hidden by a fallback owner. A repository has only * @org/platform and *.js @org/js-reviewers, while Protected path prefixes includes infra/. A pull request changes infra/main.tf and src/deploy.js. Owner-assigned coverage can look complete because both paths have owners, but Path Owner Ledger marks infra/main.tf as Baseline only. The next action is to add an /infra/ owner rule instead of treating the catch-all owner as enough.

Syntax skip before review. A CODEOWNERS draft includes !generated/ to try to exclude generated files and /packages/[ab]/ @org/pkg for a character range. Those rules are skipped, so Active rules reports skipped lines and the remediation queue shows syntax rows. Replace the unsupported patterns with accepted CODEOWNERS-style rules or move generated files into Ignored path patterns if they are intentionally outside this review.

FAQ:

Which CODEOWNERS file should I paste?

Use the CODEOWNERS content from the pull request base branch. GitHub uses the base-branch ownership file for review requests, so a feature-branch draft can give the wrong answer if it differs from the branch receiving the merge.

Why did a file show as covered but still need review work?

A file can have an owner-bearing rule and still be weakly covered. Protected paths that match only *, CODEOWNERS edits without a direct self-owner, and ownerless overrides all create remediation rows even when the percentage is above the target.

Can I paste Git output instead of a clean path list?

Yes. Changed files accepts one path per line, git status --short, git diff --name-status, tab-delimited rename rows, and simple changed-file exports. Rename rows use the new path because that is what needs ownership after merge.

Are pasted ownership files uploaded?

The analysis runs in the browser. Browsed text files are read locally, and the CODEOWNERS content and changed-file list are not sent to a server for the coverage calculation.

What should I do when the result says a CODEOWNERS line was skipped?

Fix or remove the skipped line before relying on the gate. Common causes include negation patterns that start with ! and bracket ranges such as [a-z], which are not valid CODEOWNERS syntax.

Glossary:

CODEOWNERS: A repository ownership file that maps path patterns to users, teams, or email owners for pull-request review.
Winning rule: The last matching CODEOWNERS rule for a changed path.
Catch-all owner: The broad * rule that assigns a default owner when no later specific rule wins.
Ownerless override: A matching CODEOWNERS rule with no owner, used to leave a path outside code-owner review.
Protected path prefix: A configured path prefix where catch-all coverage is treated as too broad for review readiness.
Direct owner coverage: The percentage of checked changed files whose winning rule has owners and is not the catch-all rule.

References:

About code owners, GitHub Docs.
Git diff-options documentation, Git project, updated 2026-04-20.