MailDev vs Mailcatcher
Both MailDev and Mailcatcher are excellent open-source SMTP “catchers” — you point your app at a local SMTP port, and outgoing mail is trapped and shown in a web UI instead of reaching real inboxes. They solve the same core problem in similar ways. Here's how they differ.
At a glance
| Feature | MailDev 3.0 | Mailcatcher |
|---|---|---|
| Runtime | Node.js (TypeScript) | Ruby |
| Install | npm or Docker | gem or Docker |
| SMTP catch-all | Yes | Yes |
| Web inbox | Modern React UI | Yes (classic UI) |
| HTML / text / source / headers | Yes | Yes |
| Responsive preview | Yes — resizable viewports | — |
| Inbox search | Yes + command palette | — |
| Light & dark theme | Yes | — |
| Real-time updates | WebSocket | WebSocket |
| Attachments | Yes | Yes |
| REST API | Full JSON API | Basic API |
| Relay to real SMTP | Yes + auto-relay rules | — |
| Embeddable / programmatic API | Yes (typed) | — |
| AI agent integration (MCP) | Built-in | — |
| License | MIT | MIT |
Comparison compiled in good faith from public documentation and may go out of date — check each project for the latest. Corrections welcome via a GitHub issue.
When to pick MailDev
-
You work in a JavaScript/TypeScript ecosystem and want
npm install -g maildevor a single Docker command. - You want a modern, searchable UI with responsive-email preview and a dark theme.
- You want to script your inbox from tests with a full REST API, or embed it in a Node app.
- You want your AI agent (Claude, Cursor, Codex…) to read and reason about your dev inbox via the built-in MCP server.
When Mailcatcher fits
-
Your stack is Ruby-first and you'd rather
gem install mailcatcher. - You want the smallest possible, long-established tool and don't need the extras above.
Either way, you get local email testing without spamming real users. If MailDev sounds like your fit: