fx
fx is an interactive terminal viewer and JavaScript-based processor for JSON, JSON Lines, YAML, TOML and large integers.
Two ways to use fx
fx can open a JSON file in an interactive terminal viewer for expanding objects, arrays and long strings, or pass input through JavaScript expressions and functions. It handles line-delimited or newline-separated JSON streams and can aggregate records when a whole collection is required.
Formats and numeric behavior
Alongside standard JSON, fx supports comments and trailing commas, YAML, TOML and large integers. These relaxed inputs are useful for inspecting configuration and logs, but output still needs validation before another system consumes it. Expressions and downstream tools can change types or numeric behavior even when the parser preserves a large integer.
Expression and write-back boundaries
JavaScript lowers the learning curve but allows complex transformations and custom configuration scripts. Treat them as code: use a copy, write results to a new file, compare structure, types and encoding, and only then replace a source file. Do not print production credentials into terminal history or build logs.
Maintenance note
This page was reviewed on 2026-08-23 against fx 39.2.0, interactive browsing, JavaScript processing, streaming JSON, YAML/TOML, big integers and the Windows amd64 standalone package.
Save to your cloud drive
Open the cloud drive to get the file directly, or save it for convenient access on another device.
Quark Cloud Drive
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Baidu Netdisk
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fx Windows interactive JSON viewing and filtering guide
The package is a single Windows x64 executable. Start with a small fixture without sensitive data, test streaming, and only then evaluate file saving.
Before you start
- Prepare a valid test document and a backup, keeping production keys and personal data out of the terminal and command history.
- Understand PowerShell pipelines and quoting because JavaScript expressions add another layer of syntax.
- Confirm whether input is JSON Lines, YAML or TOML rather than relying only on a filename extension.
Installation steps
- 01
Place and verify the executable
Put fx_windows_amd64.exe in a tools directory, optionally rename it to fx.exe and run a help or version command.
- 02
Choose a PATH policy
Use the full path for occasional viewing. Add the directory to the user PATH for repeated pipeline use and pin the version in scripts.
- 03
Test the interactive terminal
Open a small JSON fixture and verify tree navigation, expand/collapse behavior, long-string previews and the exit shortcut.
Quick start
- 01
Browse a JSON file
Pass a file path to fx, inspect object and array levels and confirm top-level structure and key field types.
- 02
Filter with an expression
Pipe JSON through PowerShell and use a JavaScript-style expression to read a field or map an array, printing the result before saving anything.
- 03
Process streaming records
Apply an expression to each JSON record in a stream. Aggregate only when the whole collection is required and monitor memory use.
Usage tips
- Comment and trailing-comma support helps inspect relaxed JSON, but output should be validated against the strict parser used downstream.
- Review custom configuration scripts like ordinary code and do not execute untrusted logic.
- Compare old and new files and run downstream checks before any in-place save.
Troubleshooting and uninstall
Why does PowerShell report an expression or quoting error?
Reduce the expression to one field and use PowerShell-appropriate outer single quotes. Put complex, reviewed logic in a configuration script.
Why does a large stream use too much memory?
Keep the operation streaming, avoid aggregating every record, select only needed fields and measure the expression on a controlled sample.
- Remove the program and custom configurationRemove PATH and script references before deleting the executable, and inspect user configuration for sensitive paths or logic that should not remain.
Frequently asked questions
Can fx only view JSON?
It focuses on JSON and also supports JSON streams, comments and trailing commas, YAML and TOML. Confirm the input format and current version behavior in scripts.
Does fx require a new query language?
It uses JavaScript expressions and functions rather than a separate DSL, but expressions can mutate objects or perform complex work and should be tested on a copy.
Can fx edit the original file directly?
It has save capabilities, but in-place writing can overwrite data. Write to a new file or backup first, then compare encoding, types, indentation and numeric precision.
Does the download require an extraction code?
The Quark entry does not require one; the four-character code for the Baidu entry is shown beside its download entry.