Janice is a Free app for Viewing Large JSON Files, for Developers, Data Scientists and Data Engineers
Table of Content
Let’s talk about a silent productivity killer many developers face: trying to open a 2GB JSON file in a text editor.
Spoiler: It never ends well.
JSON (JavaScript Object Notation) is the lifeblood of modern web and mobile development, used for APIs, configuration files, logs, data exports, and more. But when these files grow beyond a few megabytes, they become nearly impossible to work with using standard tools like VS Code, Sublime Text, or even dedicated JSON viewers.
The editor freezes. Your laptop fans sound like a jet engine. And eventually, you’re forced to close the app, losing any progress or context.
This isn’t just annoying, it’s a real workflow blocker.
Hazem Abbas
Developers need to inspect, search, and analyze large JSON files regularly:
- Debugging API responses from microservices
- Reviewing exported database dumps
- Validating data pipelines or ETL outputs
- Working with machine learning datasets or telemetry logs
But most tools treat JSON as plain text. They try to load the entire file into memory, syntax-highlight it all at once, and build a full parse tree, which is overkill and unsustainable for large files.
That’s where Janice comes in.
What is Janice, The JSON File Viewer?
Janice is a lightweight desktop app designed specifically for viewing and navigating massive JSON files quickly and efficiently, without crashing, freezing, or consuming all your RAM.
Instead of loading everything at once, Janice uses smart streaming and lazy-loading techniques to parse only the parts you’re interacting with. It presents the data in a clean, expandable tree structure, supports fast search, syntax validation, and even lets you extract specific paths or arrays, all while keeping memory usage low.
The app is developed by Erik Kalkoken, a Programmer, gamer and Eve Online addict.
For developers, data engineers, & data scientists, this means:
- No more “Out of Memory” errors
- Instant preview of large files (even 10GB+)
- Fast search across deeply nested fields
- Ability to explore data without writing custom scripts
- Focus on understanding the data, not fighting the tool
In a world where data keeps growing, having a reliable, performant way to inspect JSON is no longer a luxury, it’s essential.
Janice isn’t just another JSON viewer.
It’s a developer’s flashlight in the dark, tangled forest of big data.
Features
- Cross-platform
- Browse through a JSON document in classic tree structure
- JSON files can be opened via file dialog, from clipboard, dropped on the window or given as command line argument
- Supports viewing very large JSON files (>100MB, >10M elements)
- Search for keys and values in the document. Supports wildcards.
- Export parts of a JSON file into a new file or to clipboard
- Copy values to clipboard
- Single executable file, no installation required
- Desktop app that runs on Windows, Linux and macOS
- Automatic dark and light theme
Platforms
- Windows
- Linux
- macOS
Install and Run
To run Janice just download and unzip the latest release to your computer. Janice ships as a single executable file that can be run directly. You find the latest packages for download on the releases page.
Linux
We are providing two variants for installing on Linux desktop:
- AppImage: The AppImage variant allows you to run the app directly from the executable without requiring installation or root access
- Tarball: The tar file requires installation, but also allows you to integrate the app into your desktop environment. The tarball also has wider compatibility among different Linux versions.
AppImage
The app is shipped in the AppImage format, so it can be used without requiring installation and run on many different Linux distributions.
- Download the latest AppImage file from the releases page and make it executable.
- Execute it to start the app.
Tip
Should you get the following error: AppImages require FUSE to run., you need to first install FUSE on your system. Thi s is a library required by all AppImages to function. Please see this page for details.
Tarball
- Download the latest tar file from the releases page
- Decompress the tar file, for example with:
tar xf janice-0.12.3-linux-amd64.tar.xz - Run
make user-installto install the app for the current user or runsudo make installto install the app on the system
You should now have a shortcut in your desktop environment's launcher for starting the app.
To uninstall the app again run either: make user-uninstall or sudo make uninstall depending on how you installed it.
Windows
- Download the windows zip file from the latest release on Github.
- Unzip the file into a directory of your choice and run the .exe file to start the app.
Mac OS
- Download the darwin zip file from the latest release on Github for your respective platform (arm or intel).
- Unzip the file into a directory of your choice
- Run the .app file to start the app.
Tip
MacOS may report this app incorrectly as "damaged", because it is not signed with an Apple certificate. You can remove this error by opening a terminal and running the following command. For more information please see Fyne Troubleshooting:
sudo xattr -r -d com.apple.quarantine Janice.app
Build and run from repository
If your system is configured to build Fyne apps, you can build and run this app directly from the repository with the following command:
go run github.com/ErikKalkoken/janice@latest
For more information on how to configure your system for Fyne please see: Getting Started.
Tech Stack
The app is written in the Go programming language, which proven to be fast and responsive especially in dealing with large files.
License
The App is released under the open-source MIT License.
Resources & Downloads
ErikKalkoken
