The Mac-native home for
your structured data.
JSON, CSV, Markdown, YAML, TOML, and XML, opened, validated, and transformed in one native app. Tree-sitter parsing, on-device AI, and the macOS document model done right. Everything stays on your Mac.
One editor. Six grammars.
Each format gets a tree-sitter grammar, a deterministic parser, and a supplementary view tuned to its shape. Not a single text box pretending to be six.
Config, API responses, app state. The default exchange format that won.
Tabular data without the headache of a spreadsheet rewriting your dates.
Prose with just enough structure. README, docs, notes, anything.
Configuration that humans actually read and write.
Modern config for Cargo, pyproject, and friends.
Enterprise interchange, SVG, RSS, configs that refuse to die.
Stays on your Mac. No accounts. No telemetry. No cloud round-trips. The data you open never leaves the device.
Incremental parsing, not full rebuilds.
Parselet uses tree-sitter for syntax highlighting and structural parsing, integrated with Neon for incremental updates. Type a character, and only the affected nodes re-parse. The rest of the tree stays where it is. The editor is built on AppKit and TextKit 1, the same text engine Apple uses for documents that need to scale. Open large config files, generated API responses, and exported data dumps without watching a spinner.
Six tree-sitter grammars, one Neon coordinator, zero web-view detours.
Instant. No download.
Built into macOS 26 and later. Used for parse-error explanations on small contexts. Runs in the OS-managed model process. Apple's compute, your hardware, no cloud.
macOS 26+ · ~3K tokens per request · Greedy decoding
Deeper reasoning for larger contexts.
A 4-bit quantized Qwen 3.5 4B model, downloaded on first use (~3.2 GB). Runs locally on your Mac via Apple's MLX framework. Used for summarizing files larger than Tier 1's context window. Loaded on demand, released when idle.
Apple Silicon · ≥16 GB unified memory · Up to 32K context with sufficient unified memory
Two AI tiers. Both run on your Mac.
Parselet's AI features are designed around a precise privacy boundary: inference stays on your Mac. There is no API key to enter, no account to create, and no cloud inference request. The only thing that travels over the network is the one-time download of the Tier 2 model, and only if you ask for it.
The flow shows up like this in the editor. Click the red marker in the gutter to surface the AI's explanation.
Line 20: Number with decimal point but no additional digits around line 20, column 25
Cause
The value '60.' at line 20 ends with a decimal point but lacks a fractional part, which is invalid JSON syntax.
Suggested Fix
Remove the trailing period to change '60.' to '60'.
Plays by macOS document rules.
Parselet is built on NSDocument, the same document model that ships with TextEdit, Pages, and every other native macOS document app. That means autosave works, Revert to Saved works, file associations work, multi-window and multi-tab work, and QuickLook previews show your files with proper syntax highlighting before you even open them. None of this is custom UI. It's macOS doing its job because Parselet wired up the document model the way Apple intended.
- ·Autosave on by default
- ·File · Revert to Saved
- ·File associations for .json, .csv, .md, .yml/.yaml, .toml, and .xml
- ·QuickLook previews with syntax highlighting
- ·Multi-window and multi-tab via standard ⌘N and ⌘T
Real menus. Real shortcuts.
Parselet ships with a full native menu bar, not a stripped-down pseudo-menu. Standard macOS conventions you already know are wired correctly: cut, copy, paste, find, undo, redo, hide, show all. On top of that, Parselet adds a small set of operations that earn their menu-bar slots:
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File · New from Format
Six explicit starting points (json, csv, md, yaml, toml, xml). Cmd-N defaults to your last choice.
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File · Convert To
Deterministic cross-format conversion via real parsers, never AI. JSON ↔ YAML, JSON ↔ TOML, YAML ↔ TOML, CSV → JSON.
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Format · Prettify (⇧⌘F) and Minify
Per-format capability. The menu shows what's supported for the current document.
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Format Switcher toolbar dropdown
Reinterpret the current document as a different format without modifying the file. View a .json as YAML; switch back; the file is untouched.
- Standard Edit menu (cut, copy, paste, find, undo, redo)
- Standard File menu (new, open, save, save as)
- Standard Window menu (next tab, previous tab, merge all windows)
- Standard App menu (settings, hide, hide others, show all)
One price. No subscription. Yours forever.
No subscription. Buy it once. All future updates included.
Lifetime
One-time purchase for your device
Buy it once through the Mac App Store. The app keeps working, and future updates are included for life. There is no subscription, trial, upgrade SKU, or version paywall.
Available on the Mac App Store.