By the numbers

A snapshot of the CoreDNS codebase. Data collected on 2026-04-30 against commit 145029c84 on branch master.

Size

The repo is overwhelmingly Go, with markdown READMEs documenting each plugin and a small slice of YAML/proto for CI and the gRPC service.

xychart-beta horizontal
  title "Lines of code by file class"
  x-axis ["Go (incl. tests)", "Test Go", "Markdown docs", "YAML config", "Protobuf"]
  y-axis "Lines" 0 --> 200000
  bar [168982, 48970, 12545, 800, 12]

Class	Files	Lines
Go (all)	666	168,982
Go tests (*_test.go)	of which 332	48,970
Markdown (READMEs, CONTRIBUTING, etc.)	~85	12,545
YAML (CI workflows, .golangci.yml, etc.)	~25	800
Protobuf (pb/dns.proto)	1	12
Total Go (non-test)	334	~120,000

The test-to-code ratio is roughly 40%.

Where the Go code lives

Directory	.go files	Notes
plugin/ (incl. pkg/ and test/)	569	60+ in-tree plugins plus shared utilities
test/	51	End-to-end integration tests
core/	30	DNS server type, server constructors, request dispatch
request/	6	Request abstraction and ScrubWriter
coremain/	5	Bootstrap, flags, version, signal handling
pb/	2	Generated gRPC code from pb/dns.proto
Top-level	3	coredns.go, directives_generate.go, owners_generate.go

Largest source files (non-test, non-generated)

File	Lines
plugin/kubernetes/controller.go	910
plugin/kubernetes/kubernetes.go	719
plugin/forward/setup.go	(~600)
core/dnsserver/server_quic.go	(~420)
plugin/dnssec/handler.go	(~400)

Tests dominate the longest-file list — plugin/kubernetes/handler_test.go is 1,189 lines, plugin/rewrite/rewrite_test.go is 1,160, and plugin/cache/cache_test.go is 910. None of these need refactoring; large tests are the norm for plugins with rich Caddyfile syntax.

Activity

CoreDNS has a steady pulse with a long tail of dependency bumps. Over the last 12 calendar months ending April 2026:

Month	Commits
2025-05	53
2025-06	33
2025-07	32
2025-08	54
2025-09	79
2025-10	41
2025-11	62
2025-12	54
2026-01	31
2026-02	32
2026-03	89
2026-04	60

Overall the repository has 4,750 commits since first commit on 2016-03-18 and 666 unique committer email addresses.

Churn hotspots (last 90 days)

File	Commits
go.mod	67
go.sum	66
.github/workflows/trivy-scan.yaml	13
.github/workflows/scorecards.yml	12
.github/workflows/codeql-analysis.yml	11
.golangci.yml	7
.github/workflows/golangci-lint.yml	7
plugin/file/zone.go	6
core/dnsserver/server_quic.go	6
.github/workflows/go.test.yml	6

The top of the list is dominated by tooling and dependencies. The first non-tooling entry is plugin/file/zone.go, then core/dnsserver/server_quic.go — both reflect ongoing refinement of the file backend and the DoQ implementation.

Bot-attributed commits

Author	Total commits
dependabot[bot]	1,191
dependabot-preview[bot]	234
coredns-auto-go-mod-tidy[bot]	150
coredns[bot]	38

That is roughly 1,613 of 4,750 historical commits, or about 34%, attributable to bot accounts (dependabot, coredns-auto-go-mod-tidy, coredns[bot]). This is a lower bound on automated work since AI coding assistants like Copilot leave no trace in git history. Almost all bot commits are dependency upgrades.

Plugins by the numbers

• In-tree plugin count: 60 (counted in plugin.cfg).
• Plugins with metrics: 26 (each ships a metrics.go).
• Plugins with fuzz harnesses: 5 (*/fuzz.go).
• Plugins implementing Readiness: 5 (kubernetes, forward, health, ready, etcd).
• External plugins referenced from plugin.cfg: 1 (on:github.com/coredns/caddy/onevent).

Complexity

• 100 source files contain a TODO, FIXME, or HACK comment, with 224 occurrences total across the tree.
• The chain compilation in dnsserver.NewServer folds an unbounded plugin list into a single Handler. Even a 60-plugin Corefile (every in-tree plugin) compiles in microseconds.
• Average package depth from the repo root is 3 (plugin/<name>/<file>.go); the deepest is 5 (plugin/pkg/<name>/<sub>/<file>.go).

Dependencies

go.mod declares roughly 35 direct dependencies plus another ~150 indirect. Notable direct ones:

• github.com/miekg/dns — the DNS message library that everything else builds on.
• github.com/coredns/caddy — the CoreDNS fork of Caddy v1 that hosts the server type.
• github.com/prometheus/client_golang — metrics.
• github.com/quic-go/quic-go — QUIC for DoQ and DoH3.
• k8s.io/{api,apimachinery,client-go} — Kubernetes informers for the kubernetes plugin.
• go.etcd.io/etcd/client/v3 — etcd backend.
• github.com/aws/aws-sdk-go-v2/{config,service/route53,service/secretsmanager} — AWS Route53 and DNSSEC key storage.
• cloud.google.com/go (via google.golang.org/api) — Cloud DNS.
• github.com/Azure/... — Azure DNS.
• github.com/oschwald/geoip2-golang/v2 — geoip plugin.

See Reference: dependencies for the full listing.

Test coverage

Statistic	Value
Test files	332
Integration tests under test/	51
Test lines of code	~49k
_test.go to non-test ratio	~40%
CI matrix	3 Go minor versions × 1 OS (Linux); see .github/workflows/go.test.yml

CoreDNS does not publish a coverage percentage. The CI job runs go test -race ./... and asserts on success.