How are repeated parameters handled?

A key that appears more than once (for example `tag=red&tag=blue`) becomes a JSON array: `"tag": ["red", "blue"]`. A key that appears exactly once stays a plain string. When you convert JSON back to a query string, an array value is expanded back into repeated keys — or, if you turn on the bracket option, into `tag[]=red&tag[]=blue`. This is the same convention PHP, Rails, and `qs` use, so the output drops straight into most backends.

How do nested objects get encoded?

Turn on "bracket notation" and a key like `user[name]=ada` parses into `{ "user": { "name": "ada" } }`, and `user[address][city]=oslo` nests two levels deep. Converting that JSON back produces the same `user[name]=ada&user[address][city]=oslo` string. With the option off, brackets are treated as literal characters in the key name, which is what you want when a parameter legitimately contains square brackets.

What's the difference between this and the URL Query Params Extractor?

The extractor takes many URLs at once and gives you a flat table of every key/value pair plus a CSV export — it is built for auditing and bulk analysis. This tool is a single-string, two-way converter: it turns one query string into a structured JSON tree (with arrays and nesting) and back again, so you can edit, reshape, and copy. Reach for the extractor when comparing campaigns across dozens of links; reach for this when you need one query string as clean, editable JSON.

Does it decode `+` and percent-encoding?

Yes. On parse, `+` becomes a space and `%XX` sequences are decoded (so `name=Ada+Lovelace` and `q=%E4%BD%A0%E5%A5%BD` come through as readable text). On build, every key and value is passed through `encodeURIComponent`, which produces `%20` for spaces — the safest, most universally accepted form. If a percent sequence is malformed, the raw text is kept verbatim instead of crashing.

Is my data uploaded anywhere?

No. The parser, the serialiser, and the JSON formatting are plain JavaScript running in your browser tab. Nothing is sent to a server and nothing is logged. The one caveat: the query-string input is stored in the page URL so you can share a link — see the privacy note before sharing a string that contains a token or secret.

Turn a captured API request into editable JSON

You copied a GET request out of the browser DevTools Network tab and the whole payload lives in the query string: `?fields=id,name&include=author&filter[status]=active&page[size]=20`. Reading that by eye is painful. Paste it here, flip on bracket notation, and you get a clean JSON tree — `filter.status`, `page.size`, the `fields` list — that you can actually read and edit. Change `page.size` to 50 in the JSON, copy the rebuilt query string, paste it back into your HTTP client, and fire the request again. No hand-counting ampersands.

Audit and clean a UTM-laden marketing link

A link from a campaign tool arrives as `?utm_source=newsletter&utm_medium=email&utm_campaign=spring&ref=&gclid=abc123`. Parse it to JSON and the empty `ref=` jumps out immediately, and `gclid` is plainly the click ID you want to strip before re-sharing. Delete those two keys in the JSON pane, copy the minimal query string, and you have a clean link. Building UTMs from scratch instead? The UTM Builder writes them for you; this tool is for taking apart and fixing the ones you already have.

Debug a redirect that keeps dropping a parameter

A login redirect is supposed to carry `?return_to=/dashboard&plan=pro&promo=WELCOME` but users land without the promo. Paste the URL the server actually produced, parse to JSON, and compare it side by side with the JSON of the URL you expected. If `promo` is missing from the parsed object, the bug is upstream of the redirect; if it is present but the value is `WELCOME%2F`, you have a double-encoding problem — the re-encoded output here makes that obvious.

Reshape form data for a different backend

One service expects flat keys (`name=ada&role=admin`) while another wants nested brackets (`user[name]=ada&user[role]=admin`). Parse the flat string to JSON, restructure the object into a `user` block in the JSON editor, then rebuild with bracket notation on. You have migrated the encoding without touching a single percent sign by hand, and the live preview confirms the new string before you paste it anywhere.

Hand a teammate a shareable, pre-filled state

You are debugging a search page whose state lives entirely in the query string: `?q=opus&sort=recent&tags=ai&tags=tools`. Get it into the exact shape you want here, then copy the page's share link — the query-string input rides along in the URL, so your teammate opens the tool already showing the same parsed JSON. Pair it with a Slack message and they see the repeated `tags` array rendered correctly, no setup on their end.

Query String ⇄ JSON Converter

Parse a URL query string into JSON and rebuild a query string from JSON — two-way, live, with array + nested object conventions — 100% in your browser

Runs locally
Category Developer & DevOps
Best for Formatting, validating, shrinking, or inspecting code-adjacent text.

Bracket notation (nested objects + key[])

Array style

Query string

JSON

What this tool does

A two-way converter between URL query strings and JSON. Paste a query string (with or without the leading `?`) and instantly read it back as a formatted JSON object; or edit the JSON and watch the query string rebuild itself character by character. Both sides stay in sync, so you can poke at either one and immediately see the effect on the other.

It handles the messy parts that trip people up. Repeated keys like `tag=red&tag=blue` collapse into a JSON array `["red","blue"]` instead of silently dropping one. The bracket convention `a[b]=c` and `a[b][c]=d` expands into real nested objects, and `list[]=x&list[]=y` becomes an array. Percent-encoding (`%20`, `%2F`, `%E4%BD%A0`) and the `+`-for-space shorthand are decoded on the way in and re-encoded with `encodeURIComponent` on the way out, so a round trip never corrupts your data. Empty values (`flag=`) and bare keys (`debug`) are preserved rather than thrown away.

Going the other direction, a JSON object serialises back into a canonical query string: arrays become repeated keys (or `key[]`, your choice), nested objects become bracket paths, and every value is URL-safe. Bad JSON gets a clear, bilingual error pointing at the problem instead of a blank screen. Everything runs locally — no request ever leaves the tab, which matters when your query string carries a session token or an internal redirect URL you would rather not log on someone else's server.

Tool details

Input: Text + Structured content; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 10 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Developer & DevOps · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Query String to JSON Converter fits into your work

Use it in the small gaps between coding, reviewing, debugging, and shipping.

Developer jobs

Formatting, validating, shrinking, or inspecting code-adjacent text.
Preparing snippets for documentation, tickets, commits, or handoff.
Checking a small payload quickly without switching tools.

Developer checks

Run irreversible transforms like minify or obfuscate on a copy.
Keep secrets out of pasted snippets unless the tool explicitly stays local.
Use your normal tests or linter before shipping transformed code.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Turn a captured API request into editable JSON
You copied a GET request out of the browser DevTools Network tab and the whole payload lives in the query string: `?fields=id,name&include=author&filter[status]=active&page[size]=20`. Reading that by eye is painful. Paste it here, flip on bracket notation, and you get a clean JSON tree — `filter.status`, `page.size`, the `fields` list — that you can actually read and edit. Change `page.size` to 50 in the JSON, copy the rebuilt query string, paste it back into your HTTP client, and fire the request again. No hand-counting ampersands.
Audit and clean a UTM-laden marketing link
A link from a campaign tool arrives as `?utm_source=newsletter&utm_medium=email&utm_campaign=spring&ref=&gclid=abc123`. Parse it to JSON and the empty `ref=` jumps out immediately, and `gclid` is plainly the click ID you want to strip before re-sharing. Delete those two keys in the JSON pane, copy the minimal query string, and you have a clean link. Building UTMs from scratch instead? The UTM Builder writes them for you; this tool is for taking apart and fixing the ones you already have.
Debug a redirect that keeps dropping a parameter
A login redirect is supposed to carry `?return_to=/dashboard&plan=pro&promo=WELCOME` but users land without the promo. Paste the URL the server actually produced, parse to JSON, and compare it side by side with the JSON of the URL you expected. If `promo` is missing from the parsed object, the bug is upstream of the redirect; if it is present but the value is `WELCOME%2F`, you have a double-encoding problem — the re-encoded output here makes that obvious.
Reshape form data for a different backend
One service expects flat keys (`name=ada&role=admin`) while another wants nested brackets (`user[name]=ada&user[role]=admin`). Parse the flat string to JSON, restructure the object into a `user` block in the JSON editor, then rebuild with bracket notation on. You have migrated the encoding without touching a single percent sign by hand, and the live preview confirms the new string before you paste it anywhere.
Hand a teammate a shareable, pre-filled state
You are debugging a search page whose state lives entirely in the query string: `?q=opus&sort=recent&tags=ai&tags=tools`. Get it into the exact shape you want here, then copy the page's share link — the query-string input rides along in the URL, so your teammate opens the tool already showing the same parsed JSON. Pair it with a Slack message and they see the repeated `tags` array rendered correctly, no setup on their end.

Common pitfalls

Forgetting to turn on bracket notation when your string actually uses brackets. With the option off, `user[name]=ada` parses to a single flat key literally named `user[name]` — which is correct if the bracket is part of the real key, but surprising if you expected nesting. Check the toggle before reading the JSON.
Assuming numeric-looking values become numbers. A query string has no types: `page=2` parses to the string `"2"`, not the number `2`, because re-encoding a guessed number could silently change data (leading zeros, big integers). If your backend needs real numbers, cast them after parsing.
Sharing a query string that contains a secret. The input is stored in the page URL for the share feature, so a session token or signed redirect in your string ends up in the access log of wherever you paste the link. For anything sensitive, copy the JSON or query string text directly instead of using the share link.

Privacy

Parsing, serialising, and JSON formatting are all plain JavaScript that runs inside your browser tab. No query string, no JSON, and no record of what you converted is ever sent to a server. Your option choices (bracket notation, array style) are saved only in this browser's localStorage. The one caveat: for the "share link" feature, your query-string input is encoded into the page URL, so if you paste that link somewhere the destination's access log will see the string. For a query string carrying a token, session id, or signed redirect, copy the text directly rather than sharing the URL.

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Query String ⇄ JSON Converter

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Query String to JSON Converter fits into your work

Developer jobs

Developer checks

Good next steps

Real-world use cases

Turn a captured API request into editable JSON

Audit and clean a UTM-laden marketing link

Debug a redirect that keeps dropping a parameter

Reshape form data for a different backend

Hand a teammate a shareable, pre-filled state

Common pitfalls

Privacy

FAQ

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