crates.io API

Free crates.io API with no key: Rust crate metadata, versions, download counts, dependencies and repository links. CORS enabled. Tested curl example.

No API key requiredCORS enabledHTTPSFree tier

Endpoint tested and returned HTTP 200 on 19 Aug 2026

What is the crates.io API?

The crates.io API is the free, key-free registry API for Rust packages, returning crate metadata, every published version, download statistics, dependencies and repository links.

crates.io is the official Rust package registry, and its API is fully open for reads. A single crate request returns the description, licence, repository, documentation link, download totals and the complete version history.

The registry asks that automated clients send a descriptive User-Agent with contact details. This is enforced in practice — generic user agents can be blocked — so set one before building anything that polls.

Quick facts

Base URL: https://crates.io/api/v1
Authentication: No API key for reads. crates.io requires a descriptive User-Agent identifying your tool and a contact address.
Rate limit: Roughly 1 request per second for automated clients; bulk consumers should use the database dumps instead.
Pricing: Free.
CORS: Enabled — callable directly from browser JavaScript
Official docs: Read the docs

How to use the crates.io API

Every request below was executed against the live API on 19 Aug 2026, and the response shown is the real body it returned — not an illustration.

1. Fetch metadata for a Rust crate

GET https://crates.io/api/v1/crates/serde

curl

curl 'https://crates.io/api/v1/crates/serde'

JavaScript (fetch)

const res = await fetch("https://crates.io/api/v1/crates/serde");
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);

Python (requests)

import requests

res = requests.get("https://crates.io/api/v1/crates/serde", timeout=20)
res.raise_for_status()
print(res.json())

Response — HTTP 200 (truncated)

{
  "crate": {
    "id": "serde",
    "name": "serde",
    "updated_at": "2026-07-18T23:05:13.266456Z",
    "versions": [
      2817185,
      1748414,
      1746112,
      1739049,
      1731560,
      1730829,
      1729657,
      1729573,
      1728804,
      1728680,
      1476368,
      1453061,
      1387964,
      1370847,
      1336088,
      1317878,
      1311481,
      1311391,
      1310780,
      1262146,
      1246742,
      1236532,
      1232938,
      1231005,
      1227207,
      1195122,
      1155749,
      1145069,
      1138012,
      1131884,
      1127880,
      1117094,
      1057075,
      1029184,
      1005793,
      1001382,
      962580,
      947780,
      947429,
      935283,
      924082,
      881758,
      881445,
      879591,
      876663,
      876632,
      865547,
      864891,
      862726,
      859451,
      858772,
      857573,
      856339,
      855606,
      853213,
      851305,
      850113,
      850061,
      850055,
      842589,
      842403,
      842025,
      841944,
      840681,
      837934,
      837604,
      818064,
      797029,
      792938,
      792908,
      773194,
      761332,
      754405,
      752788,
      749292,
      747404,
      745129,
      744000,
      691601,
      685308,
      681082,
      676945,
      671664,
      647090,
      646778,
      626961,
      606237,
      598895,
      595739,
      594649,
      587380,
      582429,
      577052,
      541963,
      489577,
      488041,
      487064,
      475782,
      469421,
      465434,
      418637,
      416728,
      415805,

Parameters

Parameter	Type	Required	Description
`crates/<name>`	path	Required	Crate name. `serde`
`q`	string	Optional	Search query on /crates. `http client`
`per_page`	integer	Optional	Results per page on search, max 100. `10`
`sort`	string	Optional	downloads, recent-downloads, recent-updates or alphabetical. `downloads`

Response fields

crate.id / namestring: Crate identifier.
crate.descriptionstring: Short description.
crate.downloadsinteger: All-time download count.
crate.recent_downloadsinteger: Downloads in the last 90 days — a better activity signal.
crate.max_stable_versionstring: Latest stable release.
crate.repository / documentationstring: Source and docs URLs.
versionsarray: Every published version with yank status and licence.

What you can build with the crates.io API

Display the current version of a Rust crate in documentation
Compare crates by recent download activity when choosing a dependency
Audit licences across a Cargo dependency tree
Detect yanked versions in use

Common errors and how to fix them

403 or blocked

Missing or generic User-Agent.

Fix: Send a User-Agent naming your tool and a contact email, as crates.io policy requires.

404

Crate name not found.

Fix: Crate names use hyphens, not underscores, in the URL even when the Rust module uses underscores.

429

Polling too fast.

Fix: Keep to about one request per second; for bulk analysis use the published database dumps instead of the API.

crates.io API — frequently asked questions

Does the crates.io API need an API key?

No key is needed for reads, but crates.io requires a descriptive User-Agent header identifying your tool and a contact address. Requests without one can be blocked.

What is the difference between downloads and recent_downloads?

`downloads` is all-time and heavily favours old crates. `recent_downloads` covers the last 90 days and is a much better signal of whether a crate is actively used.

How do I check if a version was yanked?

Each entry in the `versions` array has a `yanked` boolean. Yanked versions remain downloadable for existing lockfiles but should not be newly adopted.

Can I use this for bulk analysis of the whole registry?

No — crates.io asks that bulk consumers use the daily database dumps rather than crawling the API, which is rate limited to about one request per second.

Tools that pair with this API

JSON Formatter

Format, beautify and minify JSON online with 2-space, 4-space or tab indentation. Sort keys alphabetically and catch syntax errors instantly — free and private.

JSON Validator

Free online JSON validator: validate JSON and find syntax errors with the exact line and column. See root type, key counts and depth — instant and 100% private.

Alternatives to crates.io API

If crates.io does not fit, these developer & testing apis cover similar ground. Every one was called before publishing, and each links to its own reference page with a working curl command and the response it returned.

API	What it does	Auth	CORS	Last verified
GitHub REST API	GitHub REST API with no key for public data: repository details, users, issues, releases and commits. 60 req/hour unauthenticated, 5,000 with a token.	No key	Yes	19 Aug 2026
JSONPlaceholder	Free fake REST API for testing and prototyping. Posts, comments, users and todos with full GET, POST, PUT and DELETE support. No key. Real curl examples.	No key	Yes	19 Aug 2026
Postman Echo	Postman Echo reflects your HTTP request back as JSON: headers, body, query params and auth. Free, no key, ideal for debugging clients. Real POST example.	No key	No	19 Aug 2026
DummyJSON	Free fake REST API with realistic products, users, carts, recipes and auth. Supports search, pagination, sorting and POST. No key. Tested GET and POST examples.	No key	Yes	19 Aug 2026
CTAN	Read LaTeX package metadata from CTAN as JSON: authors, licence, version, documentation links and descriptions. No API key. Verified example and parsing notes.	No key	No	21 Aug 2026
Debian Sources	Search Debian source packages and browse their file trees as JSON, with no key. Covers every suite from oldstable to sid. Verified example and endpoint map.	No key	No	21 Aug 2026

All Developer & Testing APIs

crates.io is an independent third-party service and is not affiliated with ByteTools or ByteVancer. Details on this page were verified on 19 Aug 2026; always check the official documentation before relying on this API in production, as terms and limits can change.