Free tools every open source maintainer should bookmark

Updated 2026-09-25 · FreeTools

In short: eight browser tools and a matching JSON API, all free with no key, no signup and no tracking. Each one solves a problem maintainers hit repeatedly: understanding a codebase, watching growth, and keeping a domain healthy.

Running an open source project means answering questions like "how big is this codebase really", "is interest growing or was that one spike", and "is the site still serving valid certificates". These tools answer each of those without installing anything.

Understanding a codebase

Count LOC

Counts lines of code in any public GitHub or GitLab repository by language, splitting code, comments and blanks, and skipping vendor and generated directories. Useful for triage: a dependency with 8,000 lines of code and 40,000 lines total is mostly generated output, and that changes how you read its maintenance burden.

curl 'https://freetools.one/v1/loc?github=torvalds/linux'

Tracking project growth

Star History

Plots cumulative stars over time for up to six repositories at once, with totals and 30-day growth per repo. The useful question is not "how many stars" but "what is the trend" — and the exportable SVG goes straight into a README:

![Stars](https://freetools.one/v1/stars/chart?github=your/repo)

Keeping the domain healthy

TLS checker

Reports protocol version, cipher strength, certificate subject, issuer, SANs and days until expiry. Renewal automation that fails silently is the classic cause of an outage, and a days_left check twice a day prevents it.

HTTP headers checker

Returns every response header plus the full redirect chain, which is how you confirm HSTS and CSP are actually deployed, and spot a redirect that adds a second of latency.

Diagnostics and data

IP geolocation

Resolves an IP or hostname to country, city, timezone and coordinates. Useful for choosing CDN regions or making sense of an unexpected traffic spike.

Weather API

Current conditions by city or by the caller's own IP, in both Celsius and Fahrenheit. It looks out of place in a developer toolkit until you wire it into a demo or an uptime page.

Random data API

Random integers, shuffled lists and names from the OS CSPRNG, for fixtures, seeding and load tests. Ten thousand values in one request:

curl 'https://freetools.one/v1/random/integer?min=1&max=6&times=10000'

CORS proxy

For debugging cross-origin requests from the browser. It is SSRF-guarded, so it is safe to point at test URLs — but do not route production traffic or secrets through it.

One API for all of them

Every tool is a plain GET endpoint, which means the whole toolkit is scriptable without an SDK. LOC and star-history results are cached for six hours, so repeated repository calls are fast; cache other responses in your application when appropriate.

# stars + LOC + certificate health in one shell loop
for repo in cli/cli BurntSushi/ripgrep; do
  loc=$(curl -s "https://freetools.one/v1/loc?github=$repo" \
        | jq -r '.[]|select(.language=="Total")|.linesOfCode')
  stars=$(curl -s "https://freetools.one/v1/stars?github=$repo" | jq '.[-1].y')
  printf '%-24s %8s LOC  %7s stars\n' "$repo" "$loc" "$stars"
done

Connect an AI agent to them

There is an MCP server at /mcp exposing six of these as native tools, plus a machine-readable API index and an OpenAPI spec. Adding one line of JSON to an MCP client gives the agent repository analysis, certificate checks and diagnostics directly.

Frequently asked questions