Ferritin — Rust documentation

Name: Ferritin — Rust documentation
Author: jbr

by jbrversion 2026.7.21i★ –iRuns in the cloud

Registry namers.ferritin/rustdoc

Install

Overview

Description from the maker (original English)

Search and read Rust documentation for the standard library and any crate on crates.io

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs in the cloud
Transport: Streamable HTTP
Category: Search & AI memory

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on the maker’s server: what you ask it goes through their server.
The registry lists no key to fill in.

You need

Runs in the cloudNothing to install; it connects over the internet

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Works in Claude on the web, desktop and mobile:

Open Settings → Connectors
Press Add custom connector
Paste the address below and press Add
If it asks you to sign in, sign in with the maker

https://ferritin.rs/mcp

Run this in your terminal

claude mcp add --transport http rustdoc https://ferritin.rs/mcp

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "rustdoc": {
      "url": "https://ferritin.rs/mcp"
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "rustdoc": {
      "type": "http",
      "url": "https://ferritin.rs/mcp"
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

ChatGPT connects only to servers on the internet:

Open ChatGPT on the web → Settings → Connectors (Apps)
Press Create or Add (some plans need Developer mode under Advanced first)
Paste the address below, give it a name and save
If it asks you to sign in, sign in with the maker

https://ferritin.rs/mcp

Menu names can differ slightly by plan and over time.

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

We have not read this server’s tool list yet; we check endpoints in rotation.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 6, 2026

✓ Pass
Maker matches the repo
The registry name was verified against the domain ferritin.rs (the registry checks domain ownership)
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
… Not checked yet
Endpoint responds
Not checked yet; we check endpoints in rotation
… Not checked yet
Sign-in with OAuth
Not checked yet; we check endpoints in rotation
… Not checked yet
No hidden instructions in tool descriptions
Not checked yet; we read the tool list when we check the endpoint

Compared with others in Search & AI memoryi

More stars than 0% of the other 7247 servers in this category
Published to the registry more recently than 24% of the other 7247 servers in this category
Basic checks equal to or better than 100% of the other 7247 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Ferritin — Rust documentation safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.

Is it still maintained?

The GitHub repo last changed –, and the latest version (2026.7.21) reached the registry 4 months ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.

What can I use instead?

In the same category: Context7, Codebase Memory, Exa

Alternatives

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Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

Context7

by upstash

Feeds AI the latest docs for libraries and frameworks before it answers, so code it writes does not use outdated, removed functions.

Computer or cloud★ 64,224MITUpdated today

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Codebase Memory

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Codebase knowledge graph for AI agents — 162 languages, sub-ms queries, 99% fewer tokens.

Runs on your computer★ 48,148MITUpdated 20 days ago

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Exa

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Connect AI agents to Exa for web search, content fetching, and multi-step research.

Runs in the cloud★ 5,213MITUpdated last month

Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

🩸 Ferritin

[][ci]

[][crate]

A terminal-based Rust documentation viewer

Ferritin reads rustdoc JSON output to display Rust documentation directly in your terminal. It supports local workspace crates, standard library documentation, and crates from crates.io, with search functionality and modern terminal features including mouse support, syntax highlighting, and clickable links.

Features

Interactive documentation browser with keyboard and mouse navigation
One-shot CLI for quick documentation lookups in the terminal
Search across crates or within specific crates
Works seamlessly across three contexts:
Local workspace crates (requires nightly toolchain)
Standard library (requires rust-docs-json rustup component)
Crates from crates.io (fetched from docs.rs on demand)
Modern terminal UI with features like italics, unicode box drawing, syntax highlighting, OSC8 hyperlinks, cursor changes in terminals that support it, and mouse hover previews
Fast navigation with history and breadcrumb trail

Installation

Prebuilt binary (recommended)

Prebuilt binaries skip compilation and are available for x86_64/aarch64 macOS, x86_64 Linux, and x86_64 Windows.

If you have cargo-binstall, it reads the release metadata and installs the right binary for your platform:

cargo binstall ferritin

Otherwise, the installer scripts detect your platform, download the matching binary, and place it in ~/.cargo/bin:

macOS and Linux:

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/jbr/ferritin/releases/download/ferritin-latest/ferritin-installer.sh | sh

Windows (PowerShell):

powershell -c "irm https://github.com/jbr/ferritin/releases/download/ferritin-latest/ferritin-installer.ps1 | iex"

Both of the above always install the most recent release. You can also pick a specific version or download archives directly from the [releases page].

From source

To build from source (or for a platform without a prebuilt binary):

cargo install ferritin

Optional: Standard library documentation

To view documentation for std, core, and alloc:

rustup component add rust-docs-json

For local workspace documentation

Local crate documentation requires a nightly toolchain:

rustup toolchain install nightly

Note: There is a relationship between ferritin's version and the nightly toolchain version. Ferritin supports a range of recent rustdoc JSON format versions, and if your nightly generates a newer format, ferritin will make a best effort at parsing it.

Usage

Interactive mode

Launch the interactive browser:

ferritin -i

Once running, use h or ? to see available keybindings. Basic navigation:

g - go to an item by path (e.g., std::vec::Vec)
s - search (Tab to toggle between current crate and all crates)
l - list available crates
Arrow keys, j/k, or mouse to navigate
Click on links to follow them

CLI mode

View documentation for a specific item:

ferritin get std::vec::Vec

ferritin get serde::Serialize

Search for items:

ferritin search "hash map"

ferritin search --crate tokio "spawn"

List available crates in your workspace:

ferritin list

Output format

Ferritin auto-detects how to render: ANSI colors on a terminal, plain text when piped, and a compact markdown-flavored format under a coding agent. Override it with --format . --format json emits a structured representation — of the resolved item for get, or of the results for search/list — for scripting and programmatic consumers:

ferritin get std::vec::Vec --format json

(The JSON shape is still settling as the library API evolves; a published JSON Schema is planned.)

Caching and Storage

Ferritin keeps its caches under a single directory — $FERRITIN_HOME if set, else $XDG_CACHE_HOME/ferritin, else ~/.cache/ferritin. Everything in it is reconstructible (fetched or derived), so it is always safe to delete:

Crates.io documentation: raw rustdoc JSON at docs/{crate}/{version}/{format-version}.json, with derived binary caches beside it (an rkyv archive for fast partial loads, and a .index file generated lazily on first search)
crates.io metadata: the crate-names artifacts (crate-names/) used for version resolution and typeahead, and per-crate version lookups (crates-io-versions/)
Standard library search indices: written to {rustc sysroot}/share/doc/rust/json/ if available
Local workspace documentation: built into the workspace's own target/doc/, not the shared cache

Earlier versions cached under $CARGO_HOME/rustdoc-json; a cache found there is migrated automatically on first run.

Environment Variables

Variable	Meaning
`FERRITIN_HOME`	Cache root override (see above)
`FERRITIN_THEME`	Default color theme (equivalent to `--theme`)
`FERRITIN_CRATE_NAMES_URL`, `FERRITIN_CRATE_DESCRIPTIONS_URL`	Override where the crate-names artifacts are fetched from (e.g. a mirror)

ferritin serve (the opt-in serve/acme features; not present in distributed binaries) is configured 12-factor style:

Variable	Meaning
`HOST`, `PORT`	Bind address (`::` binds dual-stack)
`FERRITIN_CACHE_BYTES`	In-memory crate-cache weight cap
`FERRITIN_RSS_HIGH_WATER_BYTES`	RSS guard threshold (Linux only): shed cache weight when anonymous RSS exceeds it
`FERRITIN_RATELIMIT`	Per-client `/api` requests per minute
`FERRITIN_ACME_DOMAIN`	Activates automatic HTTPS via Let's Encrypt for this domain
`FERRITIN_ACME_CACHE_DIR`	Required with ACME: persists the account key and certificates
`FERRITIN_ACME_CONTACT`	Optional ACME contact email
`FERRITIN_ACME_PRODUCTION`	Use the Let's Encrypt production directory (default: staging)

Development-only knobs (not part of the stable interface): FERRITIN_TEST_MODE (normalized snapshot-test output), FERRITIN_REINDEX (rebuild search indexes in memory, bypassing the disk cache), and the search-scoring probes FERRITIN_NAME_WEIGHT, FERRITIN_ANCESTOR_WEIGHTS, and FERRITIN_NAME_PREFIX_COUNT.

Current Status

Ferritin is at version 0.x and actively used by the author as a primary documentation interface. It's ready for general use, though the output format should be considered unstable and may change between versions.

If you're scripting against ferritin's output, be aware that the text format may change. Pin to a specific version or be prepared to update your scripts.

Platform Support

Ferritin is developed primarily on Unix-like systems and is also tested on Windows, where both the CLI and interactive TUI work (prebuilt x86_64 Windows binaries are provided). If you encounter issues on any platform, please open an issue or pull request.

Related Projects

Ferritin was originally developed to support the rustdoc-mcp MCP server, which provides Rust documentation access for Claude Code and other MCP clients.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Ferritin — Rust documentation

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Search & AI memoryi

Common questions

Alternatives

Context7

Codebase Memory

Exa

README from the maker

🩸 Ferritin

Features

Installation

Prebuilt binary (recommended)

From source

Optional: Standard library documentation

For local workspace documentation

Usage

Interactive mode

CLI mode

Output format

Caching and Storage

Environment Variables

Current Status

Platform Support

Related Projects

License