### File

JSON fileAction

stats  pretty  minify

Choose the action, then pick the file again to re-run. Stats avoids building a giant pretty string. The file is never written to localStorage.

Clear  Copy  Download

Small drafts still belong in the [JSON editor](https://www.toolcomb.com/json-editor).

### Worker result

Choose a JSON file. It is parsed off the UI thread.

# JSON File Processor - Format, Minify and Inspect JSON Files

Choose a JSON file to format, minify, or inspect its structure in your browser. Files up to 50 MiB are accepted; available memory and processing time can limit what your device handles.

## What Is a JSON File Processor?

A **JSON file processor** is a browser tool that reads a `.json` file from disk, parses it off the UI thread, and returns either structure counts or a rewritten string - pretty-printed or minified. It exists because textareas and localStorage are the wrong place for a 20 MB API dump. Browser quota for localStorage is around 5 MB per origin. Expanding every node of a huge tree will freeze the tab. This page never writes the payload to localStorage.

The documented cap is **50 MB**. Some devices will fail sooner. That is an honest browser limit, not a streaming GB parser and not an mmap of a 2 GB warehouse dump. The worker still holds the full string and the parsed value in RAM. If you need gigabyte logs, use jq, a local script, or a database - not a tab.

Stats mode counts nodes, objects, arrays, and keys after parse without necessarily building a pretty-printed twin of the file. Pretty and minify return a string you can download. The on-page preview truncates very large pretty output so the DOM does not paint a million characters. NDJSON (one value per line) is not a single `JSON.parse`. Concatenating logs will fail.

The worker has a 30 second timeout. Pathological nesting can still exhaust memory. This is not jq, not a database, and not an NDJSON grep. Query a sample on the JSON query tool after you cut the file down. Repair of broken drafts belongs on JSON repair for small text, not inside this worker.

## How to Process a Large JSON File Locally - Step by Step

Processing a file stays on your machine:

1. **Choose stats, pretty-print, or minify** - Stats counts nodes, objects, arrays, and keys after parse without necessarily building a giant pretty string. Pretty and minify return a downloadable JSON string.
2. **Select a .json file** - The file is processed in your browser. Files over 50 MiB are rejected; files within the limit can still exceed your device's memory or processing time.
3. **Wait for the Web Worker** - Parse runs off the UI thread with a 30 second timeout. If the file is not JSON, the worker returns an error string instead of hanging the page.
4. **Download or copy the result** - Stats appear as counts. Pretty and minify can be downloaded. The on-page preview truncates very large strings; download for the full file. Closing the tab drops the in-memory copy.
5. **Re-run with a different action** - Change stats / pretty / minify, then choose the file again. The last action is remembered; the file bytes are not.
6. **Split or repair if the worker fails** - Over-cap files must be split locally. Broken JSON should be repaired as a small draft, not as a 40 MB blob in this textarea-free page.

## JSON File Processor Example - Stats vs Pretty vs Minify

Suppose you select a small export that looks like this on disk (minified, one line):

```
{"users":[{"id":1,"name":"Ada"},{"id":2,"name":"Grace"}],"ok":true}
```

### Stats action

The worker parses once, walks the tree, and returns counts. You get nodes, objects, arrays, and keys without building a second copy of the file as indented text. That is the right first pass on a 30 MB dump when you only need to know how bushy it is.

### Pretty action

```
{
"users": [
{ "id": 1, "name": "Ada" },
{ "id": 2, "name": "Grace" }
],
"ok": true
}
```

Download `pretty.json`. The preview may truncate; the download is the full string. Pretty-print of a 50 MB value can hitch when the string returns to the page - that is why stats exists.

### Minify action

Minify creates compact JSON that you can download as `minified.json`. The file is parsed and written again: duplicate object keys can collapse, very large integers can lose precision, and number formatting can change. Keep the original when exact representation matters.

## When You Need a File Processor - Real-World Use Cases

### Inspecting a production API dump without uploading it

Support and backend teams often download a JSON export that is too large for a paste box. This page reads the File locally, so the dump never crosses the network. Stats tells you whether the file is a huge array, a nested object, or both before you decide to pretty-print.

### Pretty-printing a minified export for a one-off review

Warehouse extracts and backup files are often one line. Pretty-print in the worker, download the result, then open a slice in an editor. Do not restore that pretty string into localStorage; that is the failure mode this tool is designed to avoid.

### Minifying a formatted dump before you attach it

Reduce formatting whitespace in a JSON export before sharing it. Download the compact result and check it against the original, especially if it contains duplicate keys or very large integer values.

### Estimating shape before you write a parser

Node, object, array, and key counts are a cheap sketch of the document. A file with millions of nodes and few objects is probably a giant array of primitives or short records. A file with many objects and keys is a nested config or a graph. That sketch belongs here, not in a frozen textarea.

### Keeping secrets off a formatter that persists drafts

Other JSON tools on this site may persist textarea drafts for 30 days. A customer export should not land there. This processor stores only the last action preference and the panel width - never the file bytes.

### Rejecting files that would freeze the tab

Files larger than 50 MiB are rejected. Files within the limit can still exceed available memory or take too long on some devices. For a larger dataset, prepare a smaller valid JSON sample locally.

### Checking that an export is actually JSON

Logs named `.json` are sometimes NDJSON or concatenated objects. The worker’s `JSON.parse` will fail with a message. That is the signal to split lines in a script, not to paste the blob into a repair tool that expects a small draft.

### Preparing a smaller sample for query or schema tools

After you know the file is valid JSON, cut a sample and use [JSON query](https://www.toolcomb.com/json-query) or [JSON Schema](https://www.toolcomb.com/json-schema-validator) on a slice. This page is the intake step for large files, not a JSONPath engine and not a contract checker.

## File Processor vs Editor vs Formatter vs jq

Pick the tool that matches the size and the job. Stretching the wrong UI is how tabs freeze:

| Need | This processor | JSON editor / formatter | jq / local script |
| --- | --- | --- | --- |
| File under a few hundred KB | Works | ✓ better UX | Optional |
| 10–50 MB single JSON value | ✓ | Will struggle | Also fine |
| Gigabyte dump / NDJSON logs | No | No | ✓ |
| Persist draft in localStorage | Never the file | Typical | Disk files |
| Count nodes without pretty-print | ✓ stats |  | Custom |
| JSONPath query |  | Query tool | jq |
| Off-UI-thread parse | ✓ worker | Usually main thread | OS process |
| Upload to a server | No | No (on this site) | No |

The general rule: **editor for drafts, processor for large files, jq for everything bigger than RAM in a tab.**

## Common File-Processor Errors - Size, Parse, Timeout

These are the failures this page reports on purpose. They are better than a frozen tab:

- **Over the 50 MB cap.** The File API still lets you pick a huge file. This page refuses it with a megabyte size message. Split the file locally.
- **JSON.parse failure.** Trailing commas, NDJSON, concatenated objects, and truncated downloads fail inside the worker. You get the error string. Repair small drafts elsewhere.
- **Worker timed out.** Thirty seconds. Pathological nesting or a machine under memory pressure can miss the window. Cut the file down.
- **Worker is not ready.** Rare; reload if the blob URL for the worker did not start. The worker is created on mount.
- **Preview truncation is not data loss.** The on-page pretty view may stop at 20,000 characters. Download for the full string.
- **NDJSON is not one value.** One JSON value per line is a different format. Concatenating lines is not `JSON.parse`.
- **Memory exhaustion.** The cap is documented, not a hard VM guarantee. Some phones will fail below 50 MB. That is still a browser limit.
- **Choosing pretty on a 40 MB file.** Parse may succeed and stringify may hitch when the result returns. Prefer stats first.

## Privacy & Security - File API, Worker, No localStorage Dump

The selected file is read with the File API and parsed in a Web Worker on your device. Nothing is uploaded. Closing the tab drops the in-memory copy. That is the privacy model for customer exports, auth dumps, and internal backups.

This page stores the last action (stats, pretty, or minify) and the panel width under unique keys. It does **not** write file content to localStorage. Click Clear to drop the in-memory name, size, stats, and output. Pick the file again if you need another pass. Do not leave a sensitive export on screen on a shared computer.

## Frequently Asked Questions

### How large a JSON file can I process?

The documented cap is 50 MB. Some devices will run out of memory sooner. This is not a streaming GB parser and will not mmap a 2 GB dump in a tab. Split huge files locally before you open them here.

### Why not use the JSON editor or formatter?

The editor and formatter hold the document in a textarea and typically persist drafts in localStorage. Browser quota for localStorage is around 5 MB per origin. A 20 MB API dump does not belong there. This page reads a File, parses in a Web Worker, and never writes the payload to localStorage.

### Does the file leave my computer?

The tool processes the selected file in your browser and does not upload it for processing. Browser extensions, shared devices and downloaded copies may still expose its contents.

### What if parse fails?

You get the worker error string. Repair small drafts on JSON repair; this processor expects a complete JSON value, not NDJSON lines unless you wrap them yourself. A trailing comma or concatenated log lines will fail JSON.parse inside the worker.

### Can I pretty-print NDJSON?

Not as a single JSON.parse. NDJSON is one value per line. Concatenating lines is a different job. Split lines in a local script, or wrap them into a JSON array first, then process the array here if it still fits under 50 MB.

### Will pretty-print of a huge file freeze the UI?

The parse runs in a worker. Serializing a 50 MB pretty string can still hitch when it returns to the page. Stats-only mode avoids building a giant output string. The on-page preview truncates very large pretty output so the DOM does not paint a million characters.

### Why is the file not saved in localStorage?

localStorage is the wrong place for a multi-megabyte dump. Quota is small, the UI thread would freeze on restore, and you would be writing a copy of a file that already lives on disk. This page stores only the panel width (and optionally the last action), never the file bytes.

### What do stats mode counts mean?

After parse, the worker walks the value and counts nodes, objects, arrays, and keys. Nodes include every value visited. Objects and arrays are structural. Keys are the number of object properties seen, not unique names across the file. Stats mode does not require building a pretty-printed twin.

### Is this a streaming parser for gigabyte dumps?

No. The worker still holds the full string and the parsed value in RAM. The 50 MB cap is an honest browser limit, not a marketing understatement of a streaming engine. For gigabyte logs use jq, a local script, or a database - not a tab.

### Is this JSON file processor free?

Yes. No signup and no upload quota, because there is no upload. Process files you are willing to hold in RAM, then download pretty or minified output when the worker finishes.

## Related JSON File & Editor Tools

After a large file is valid JSON, smaller tools finish the job:

- [JSON Editor](https://www.toolcomb.com/json-editor) - Textarea drafts and table mode for documents you are willing to keep in the page.
- [JSON Formatter](https://www.toolcomb.com/json-formatter) - Pretty-print small payloads with live preview. Do not paste a 40 MB dump there.
- [JSON Minifier](https://www.toolcomb.com/json-minifier) - Compress formatted JSON in a textarea when the file is small enough to paste.
- [JSON Repair](https://www.toolcomb.com/json-repair) - Heuristic fixes for small broken drafts, not for NDJSON logs.
- [JSON Validator](https://www.toolcomb.com/json-validator) - Line and column syntax check for text you paste, not for 50 MB files.
- [JSON Query](https://www.toolcomb.com/json-query) - JSONPath on a sample after you cut the file down.
- [JSON Schema Validator](https://www.toolcomb.com/json-schema-validator) - Contract check on a slice, not on the whole dump in this worker.
- [JSON Viewer](https://www.toolcomb.com/json-viewer) - Interactive tree for documents that fit in memory as a UI tree.

## Related Tools

Discover more free tools that might help with your next task.

[JSON Formatter Format and validate JSON data Use Tool](https://www.toolcomb.com/json-formatter)

[JSON Viewer View JSON data in a tree structure Use Tool](https://www.toolcomb.com/json-viewer)

[JSON Minifier Minify JSON data to reduce size Use Tool](https://www.toolcomb.com/json-minifier)

[JSON Editor Edit JSON in text, tree, and table modes. Works offline in the browser Use Tool](https://www.toolcomb.com/json-editor)

[JSON Query Query and transform JSON with JSONPath Use Tool](https://www.toolcomb.com/json-query)

[JSON Compare Diff two JSON documents path by path Use Tool](https://www.toolcomb.com/json-compare)

[View All Tools](https://www.toolcomb.com/tools)