markjason
.md and .json, nothing else.
the fastest way to read specs, edit prompts, and manage configs.
built for the only human tasks in agentic coding.
Built for the AI era
Your agents write code. You manage the artifacts.
Capture agent output
Paste from clipboard → auto-detect format → instant preview. The fastest path from Claude to readable.
Actually instant
0.3 seconds cold start. 100MB RAM.
Not "fast for an Electron app." Actually fast.
Insta-copy everything
ENV value? Click. Filename? Click or ⌃⌘C.
Your agent asks "which file?" You know what to do.
Live sync with your agents
When something else edits the file, you see it.
No reopening, no refresh, just there.
JSON you can read
Collapsible tree. Types color-coded. Search with ⌘F.
Error? Click it. Jump there.
Raw ↔ Read
One key. Toggle between editing and previewing.
Scroll position? Preserved. Sub-line precision.
Keyboard first
⌘K quick open. ⌘B bold. ⌘⇧M syntax help.
Your hands stay where they belong.
Share as image
One click to export any file as a clean, shareable image.
Send specs to non-technical colleagues. No screenshots.
Why not just use VS Code?
VS Code
- Open app
- Wait for extensions
- Wait for language server
- Read and edit your file
- Wonder why that took 2GB of RAM
markjason
- Double-click file
- Read and edit
- 100MB RAM 🧘
What we'll never add
Get it
Free. No account. No tracking. Just an app.
View on GitHub — install instructions & troubleshooting
Pro tip: After installing, right-click any .md or .json file → Get Info → Open with → markjason → Change All.