# Codeharbor

> A coding IDE in your browser: edit, preview and run web projects safely, then share them. Codeharbor is a small coding IDE that runs in your browser: a file tree, tabs and split view, an accessible editor with syntax highlighting for 15 languages, find and replace, a command palette and live problems for JSON, YAML, JavaScript and TypeScript. Web pages and scripts run in a sandbox on a separate address, with their console output shown in the IDE. Projects stay in your browser with snapshots, commits and ZIP export, or are shared in a Teamspaces workspace where teammates’ changes merge file by file.

Codeharbor (Coding IDE) is an app of usefulweb.app (https://usefulweb.app/): a full program that runs in the browser. Its engine is deterministic and the same functions are exposed as tools, so an agent can compute exactly what the app shows.

## Use it
- Landing page: https://codeharbor.usefulweb.app/
- Workspace (browser app): https://codeharbor.usefulweb.app/app - open a project with https://codeharbor.usefulweb.app/app#project=<base64url-encoded project JSON> or a template with https://codeharbor.usefulweb.app/app#template=<id>
- Project file format (JSON Schema): https://codeharbor.usefulweb.app/project.schema.json
- Tutorials: https://codeharbor.usefulweb.app/tutorials
- JSON API: POST https://codeharbor.usefulweb.app/api/v1/tools/<toolId>/calculate (catalog: https://codeharbor.usefulweb.app/api/v1/tools)
- OpenAPI: https://codeharbor.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://codeharbor.usefulweb.app/mcp

## Engine tools
- [Codeharbor Format & Check](https://codeharborformat.usefulweb.app/): Format JSON, CSS and HTML and find syntax errors in JSON, YAML, JavaScript and TypeScript. Part of [Codeharbor](https://codeharbor.usefulweb.app/) (ownerApp: codeharbor). API: POST https://codeharbor.usefulweb.app/api/v1/tools/codeharbor-format/calculate · MCP tool `codeharbor_format`
- [Codeharbor Diff](https://codeharbordiff.usefulweb.app/): Compare two texts line by line and get a unified diff with added and removed lines. Part of [Codeharbor](https://codeharbor.usefulweb.app/) (ownerApp: codeharbor). API: POST https://codeharbor.usefulweb.app/api/v1/tools/codeharbor-diff/calculate · MCP tool `codeharbor_diff`
- [Codeharbor Markdown Preview](https://codeharbormarkdownpreview.usefulweb.app/): Render Markdown to safe HTML with an outline, word count and heading checks. Part of [Codeharbor](https://codeharbor.usefulweb.app/) (ownerApp: codeharbor). API: POST https://codeharbor.usefulweb.app/api/v1/tools/codeharbor-markdown-preview/calculate · MCP tool `codeharbor_markdown_preview`

## Formats
- Import: Codeharbor project (.codeharbor.json), ZIP archive of a folder (stored or deflated entries), Single text files (any of the supported languages), Project link (#project=)
- Export: Codeharbor project (.codeharbor.json), ZIP archive with folders, Single file download, Unified diff (.diff), Rendered Markdown as HTML

## Limits
- No npm packages, no terminal, no Git remote, no language server or code completion.
- Python, shell, SQL, Rust, Go and C are not run in the browser; export the project and run it on your computer.
- Syntax checks for JavaScript and TypeScript are basic (tokens, brackets, a few statement rules); there is no type checking.
- TypeScript enums, namespaces, decorators and parameter properties are not supported by the type stripper; JSX is not transformed.
- Projects are limited to 400 files, 1 MB per file and 8 MB in total.
- Loops in previewed pages are stopped after about two seconds of continuous running; long synchronous computations belong in a script run.
- Live collaboration merges whole saves file by file, not keystroke by keystroke.