Find a tool

Query String Builder Runs in your browser. No input data is sent to our server.

Paste one key=value pair per line, build the query string instantly, and copy the finished result. This page is useful for redirects, campaign links, app integrations, API testing, and developer workflows.

Built query string

Paste content and run the tool instantly.

This tool runs entirely in your browser, so you can inspect, transform, or generate developer text without sending it to a remote processing service.

Build Query Strings Online

Build URL query strings from key-value pairs for redirects, tracking links, APIs, campaign URLs, and browser debugging. Enter one key=value pair per line and the tool percent-encodes each value and assembles the correctly formatted query string — useful for constructing UTM links, OAuth redirect URLs, API request parameters, and any URL that requires encoded values.

How to use Query String Builder

1

Paste content into the parameters input panel.

2

Run the tool to generate the built query string.

3

Copy or download the result once it looks right.

Why this helps in real workflows

Building a tracking link with UTM parameters for a campaign without manually percent-encoding values.

Constructing an API request query string from a list of parameters before pasting it into a URL.

Creating a redirect URL with multiple encoded parameters for an OAuth or SSO flow.

Testing how a URL changes when certain parameters are added or modified.

Common problems and fixes

Special characters in values are breaking the URL.

The builder encodes keys and values automatically. Spaces become %20, ampersands become %26, and slashes become %2F — no manual encoding needed.

I need the same key with multiple values.

Repeat the key on separate lines: quality=90 on one line and quality=80 on the next. The builder outputs both as separate parameters.

The output doesn't include a leading question mark.

The builder outputs the encoded query string starting with '?'. If you need to append it to a URL, paste it directly after the path.

Related tools

Developer Tools Hub Query String Parser URL Parser URL Encoder cURL Converter Markdown Editor & Preview Lorem Ipsum Generator UUID / ULID Generator QR Code Generator SLA Uptime Calculator SLO Error Budget Calculator Hash Generator HMAC Generator Slug Generator Word & Character Counter Case Converter Text Sorter & Deduplicator JSON Diff & Merge JSON Schema Generator BCrypt Hash Generator BCrypt Hash Verifier Diff Checker JWT Decoder JSON Minifier Unix Timestamp Converter Timezone Converter Date Difference Calculator Time Now Color Code Converter CSS Gradient Generator Number Base Converter

Related Guides

How Query Strings Work in URLs How Query Strings Help Tracking and Redirects What Is Base64URL and When Is It Used?

Frequently asked questions

How do I build a query string?

Paste one key=value pair per line into the input box, run the builder, and copy the generated query string.

Does this query string builder encode special characters?

Yes. Keys and values are URL-encoded automatically — spaces, slashes, ampersands, and other reserved characters are all encoded correctly.

Can I add the same key multiple times?

Yes. Put each key=value pair on its own line. Duplicate keys are all included in the output as separate parameters.

What format should I use for input?

One key=value pair per line. For example: from=png on the first line, to=jpg on the second. Lines without an equals sign are ignored.

What's the difference between this and the URL encoder?

The URL encoder percent-encodes a raw string. This builder takes structured key=value pairs and produces a properly formatted query string with encoding applied to each value.

Is this query string builder free?

Yes. It is free to use in your browser.