jless — Command-Line JSON Viewer with Interactive Navigation

Introduction

jless is a terminal-based JSON viewer that renders JSON data as a collapsible tree you can navigate, search, and explore interactively. It fills the gap between piping JSON through jq for extraction and opening files in a text editor for manual inspection.

What jless Does

• Displays JSON as an interactive, collapsible tree in the terminal
• Supports vim-like key bindings for navigation (j/k/h/l)
• Provides search functionality to locate keys and values
• Handles large JSON files efficiently with lazy rendering
• Supports YAML input in addition to JSON

Architecture Overview

jless parses input into a tree data structure and renders visible nodes to the terminal using a TUI framework. Navigation moves a cursor through the tree without re-parsing. Collapsed subtrees skip rendering entirely, allowing large documents to remain responsive. The search function walks the tree and highlights matching nodes.

Self-Hosting & Configuration

• Install via Homebrew, Cargo, or download prebuilt binaries for Linux and macOS
• No configuration file is needed; jless works out of the box
• Pass files as arguments or pipe JSON through stdin
• Use --mode line for a flat line-based view instead of the tree
• Supports reading from compressed files when piped through zcat or similar

Key Features

• Collapsible tree view with expand/collapse on individual nodes
• Vim-style key bindings including gg, G, Ctrl-d, Ctrl-u for fast navigation
• Regex-based search with n/N to jump between matches
• Data mode that shows raw values vs. line mode for source-level view
• Handles deeply nested documents without performance degradation

Comparison with Similar Tools

• jq — Powerful JSON processor for filtering and transforming, not an interactive viewer
• fx — Interactive JSON viewer with JavaScript-based filtering, heavier runtime
• gron — Flattens JSON to greppable lines, no tree view
• bat — Syntax-highlighted file viewer, no JSON-specific navigation or collapse

FAQ

Q: Does jless support editing JSON? A: No. jless is read-only. Use jq or a text editor to modify JSON data.

Q: Can jless handle very large files? A: Yes. jless uses lazy rendering so only visible nodes are drawn, making it responsive even with multi-megabyte files.

Q: Does it support YAML? A: Yes. jless auto-detects YAML input and renders it as a navigable tree.

Q: How do I copy a value from jless? A: Press y to yank the value at the cursor position to the system clipboard (where supported).

Sources

• https://github.com/PaulJuliusMartinez/jless
• https://jless.io