Convert.Online MCP Server

Convert files between 400+ formats — images, video, audio, documents, spreadsheets, ebooks, fonts, CAD and 3D — from inside a conversation with an AI assistant. 37,500 conversion pairs, OCR, and no account needed to try it.

There are two ways in, and they expose the same five tools.

Hosted — nothing to install, nothing to run:

https://mcp.convert.online

Local — for clients that launch a command rather than speak OAuth to a URL:

npx -y convert-online-mcp

What this repository is. Two things: the stdio server in src/, MIT-licensed and published to npm as convert-online-mcp, and the documentation for the hosted endpoint. The local server is a thin client — it calls the public REST API and converts nothing itself, so no file ever passes through it. The conversion pipeline behind both is convert.online and is not open source. Issues and questions are welcome here.

Connect

OAuth (recommended)

Clients with connector support — Claude, ChatGPT and others — need only the URL. The server supports dynamic client registration, so nothing has to be provisioned in advance: add https://mcp.convert.online as a custom connector and approve the sign-in when it appears.

The flow is authorization code with PKCE (S256 required). Access tokens last one hour, refresh tokens ninety days, and every connected application can be revoked from the account dashboard — revocation takes effect immediately for both tokens.

Discovery metadata:

API key

Clients configured from a file can send a key instead. Create one at Dashboard → API Keys.

examples/claude-desktop.json:

{
  "mcpServers": {
    "convert-online": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote", "https://mcp.convert.online",
        "--header", "Authorization: Bearer YOUR_API_KEY"
      ]
    }
  }
}

Any MCP client works the same way: point it at https://mcp.convert.online and send Authorization: Bearer YOUR_API_KEY.

Local stdio server

Clients that launch a command — Cursor, Zed, Continue, and anything reading a config file — can run this package instead, with no mcp-remote shim in between:

{
  "mcpServers": {
    "convert-online": {
      "command": "npx",
      "args": ["-y", "convert-online-mcp"],
      "env": { "CONVERT_ONLINE_API_KEY": "YOUR_API_KEY" }
    }
  }
}

It needs Node 18 or newer, and nothing else. Files are never read by this process: a source given as source_url is fetched by our server, and a local file is uploaded straight to storage from wherever you run the PUT.

Building from source: npm install && npm run build, then node dist/index.js.

Related MCP server: ChangeThisFile MCP Server

Tools

Five, and the annotations are set so a client can reason about them before calling.

list_formats — read-only

Lists supported formats. With no argument, every input format; with input_format, the formats that one converts to.

list_options — read-only

Lists the settings a given conversion accepts — resize, quality, codecs, bitrate, trim, crop — with their exact names, so convert can be called with settings that exist rather than guessed.

create_upload

Returns somewhere to put a local file. The right choice for any file that is not already at a URL, whatever its size: it hands back an upload URL and an import_id. PUT the bytes to that URL, then pass the import_id to convert.

convert — not read-only, open-world

Converts a file and returns a download link. Takes one of source_url (any URL the server can fetch) or import_id (from create_upload).

options is keyed by the names list_options returns for that pair.

get_job — read-only

Status of a conversion job, and its download link once finished.

A worked exchange

You: Convert these HEIC photos to JPG.

The assistant calls convert with input_format: "heic", output_format: "jpg", and gets back:

Conversion finished.
Download: https://convert.online/download/…
Job id: 7f3c9a2e…

For a file already on the web, one call is enough:

{
  "source_url": "https://example.com/report.docx",
  "output_format": "pdf"
}

For a local file it is three: create_upload → PUT the bytes → convert with the import_id.

The same engine over REST

Everything the MCP server does is also a plain HTTP API, and the server builds exactly the same job envelope internally — a job is a named chain of tasks:

{
  "tasks": {
    "import-1": { "operation": "import/upload" },
    "convert-1": {
      "operation": "convert",
      "input": "import-1",
      "input_format": "heic",
      "output_format": "jpg"
    },
    "export-1": { "operation": "export/url", "input": ["convert-1"] }
  }
}

Note that tasks is an object of named steps, not an array — each step refers to the one before it by name, which is what lets a job branch.

• OpenAPI 3.1 — https://api.convert.online/openapi.json

• API documentation — https://convert.online/api-docs

• Authentication, all three levels — https://convert.online/auth.md

• Job Builder, which writes the request for you — https://convert.online/api-job-builder

See examples/rest-quickstart.md for the five calls end to end.

Limits and cost

A free tier exists and needs no credit card. Anonymous conversion through the website needs no account at all. Quotas and paid plans are at convert.online/plans.

License

The documentation and examples in this repository are MIT licensed — see LICENSE. The hosted service has its own terms and privacy policy.