Large JSON Viewer
Open large JSON and NDJSON files in your browser and search them locally. Read-only viewing with line numbers, full-text search by key, value or path, jump-to-match, and exports — no upload.
Upload a JSON or NDJSON file
Files are processed entirely in your browser. Nothing is uploaded.
.json · .ndjson · .jsonl · .jsonlines
Key Features
Read-only JSON viewing
Open large JSON and NDJSON files as read-only text with line numbers and a scrollable viewport. The file is rendered locally; nothing is edited or uploaded.
Line numbers & virtual scroll
Every line is numbered and the viewport only renders visible rows, so even multi-megabyte documents open and scroll smoothly without loading the whole file into the editor.
Local full-text search
Search the document by key, value or path inside a Web Worker, with case-sensitive matching, a live progress bar and a cancel button. The main thread stays responsive.
Regular-expression search
Flip the .* toggle to search with a regular expression. The pattern is validated while you type, so syntax errors surface immediately, and shapes prone to catastrophic backtracking (such as (a+)+) are rejected before they can freeze the page.
Structure overview
Open the structure panel to see the root type, the maximum nesting depth and a count of every JSON type (object, array, string, number, boolean, null) — a quick way to get oriented in an unfamiliar file.
Jump to matches
Each match reports its line, column and character offset. Use previous/next to move between matches and the viewer scrolls straight to the matching line and highlights it.
Context lines & copy
For the current match, see the surrounding lines (before and after) and copy that context to the clipboard for reference or reporting.
Export matches
Export the matched lines as TXT, JSON or CSV. For record-style JSON or NDJSON you can also export the record array as CSV, the same output the JSON to CSV tool produces.
Private & client-side
All reading, searching and exporting happen in your browser. The file is never uploaded to a server.
JSONPath, node preview & paging
Copy a match's JSONPath, open a local pretty-printed preview of the matched node, and step through top-level array or NDJSON items with a pager — all without building a full node index.
How to Use
Open a file
Drag a .json, .ndjson, .jsonl or .jsonlines file into the drop zone, or use the choose-file button. You can also open a file from another tool when it is too large for inline editing.
Browse the read-only view
Scroll through the document with line numbers. Turn on wrap to fold long lines, or leave it off so very long lines are protected and shown in full only when you expand them.
Search keys, values or paths
Type a query and pick whether to match values, keys or paths. Enable case-sensitive matching when needed, or turn on the .* toggle to search with a regular expression. Searching runs in a Web Worker with a progress bar you can cancel. Use the structure button for a quick overview of the document's shape.
Jump, inspect and export
Click a match to jump to its line, review the surrounding context, and copy or export the matches as TXT, JSON or CSV.
Viewing and Searching Large JSON Locally
What This Tool Does
The Large JSON Viewer opens JSON and NDJSON files in your browser and lets you read and search them locally. It is a read-only viewer: it does not edit, pretty-print or minify the document. That focus keeps it fast and predictable for big files.
Why a Separate Viewer
Standard editors parse the whole document into memory so you can edit it. For very large files that blocks the page. This viewer streams the file in a Web Worker, shows it as numbered read-only text, and searches it there too — so the main thread stays responsive.
Reading the Document
The viewport renders only the visible rows, with a line number for each line. Wrap folds long lines; with wrap off, very long lines are protected and can be expanded individually so the page never tries to lay out one giant line. The structure button reveals the root type, the maximum nesting depth and a count of each JSON type, which helps when you open a file you have never seen before.
Searching
You can search by value, key or path, and matching can be case-sensitive. Turn on the .* toggle to search with a regular expression: the pattern is validated while you type, syntax errors are reported immediately, and patterns prone to catastrophic backtracking are rejected instead of being run. Either way the search runs in a Web Worker with a progress bar and a cancel button, so you can stop a search on a huge file at any time.
Jumping and Context
Every match carries its line, column and character offset. Click a match or use previous/next to move through them; the viewer scrolls to the line and highlights the match. The surrounding lines are shown as context, and you can copy that context.
Exporting
Matched lines can be exported as TXT, JSON or CSV. For record-style data (a JSON array of objects or an NDJSON stream) the records can also be exported as a CSV table — the same output the JSON to CSV converter produces.
Privacy
Everything happens in your browser. The file is opened, searched and exported locally and is not uploaded to a server. Still avoid pasting secrets you would not open in any local application.