URL Encoder / Decoder

Safely encode and decode URLs and query parameters. Features batch processing, RFC 3986 compliance, and a live query parser.

Developer Tools, Encoding & Decoding (sub)

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Strictness:

Use + for spaces (form-encoded)

Input

Output

Tech Specs & Security

Processing: 100% Client-side JS API

Max Input Size: Unlimited (Browser-based)

Browser Support: All modern browsers

What is the URL Encoder / Decoder?

URL Encoder / Decoder is a specialized developer utility designed to handle percent-encoding (also known as URL encoding) for safe data transmission via HTTP. Because URLs can only contain a specific set of ASCII characters, reserved symbols like spaces, ampersands, and slashes must be mathematically escaped into '%' prefixed hex codes. URL Encoder / Decoder allows users to choose between strict parameter encoding and loose full-URL encoding to ensure data integrity. Designers and developers use URL Encoder / Decoder to sanitize query strings, clean up tracking parameters, and verify encoded JSON payloads before sending them to an API.

Strictness: encodeURI vs. encodeURIComponent

Understanding when to use different encoding levels is essential for web development. URL Encoder / Decoder provides a 'Strictness' selector to toggle between two core behaviors. The 'Parameter (Strict)' mode uses the encodeURIComponent algorithm, which escapes every non-alphanumeric character, making the result safe for injecting into a key-value pair. The 'Full URL (Loose)' mode uses the encodeURI algorithm, which preserves structural characters like slashes, colons, and question marks so the address remains routable by the browser.

Space Handling and Form Encoding

URL Encoder / Decoder includes a dedicated toggle for space character formatting. Under modern RFC 3986 standards, spaces are typically converted to '%20'. However, legacy HTML forms and certain backend systems require the '+' symbol instead. Users can easily switch between these two formats in URL Encoder / Decoder, ensuring that generated URLs are perfectly compatible with the target server or legacy application requirements.

Live Query Parameter Parser

Decoding a long, messy URL with dozens of tracking parameters can be overwhelming. URL Encoder / Decoder features a specialized query parser that automatically detects UTM tags, search queries, and session IDs during the decoding process. A structured table appears below the output, separating every key and value into readable rows. This allows SEO professionals and marketers to audit complex URLs instantly without manually scanning through percent-encoding noise.

How to Use the URL Formatter

Select the mode: use the toggle at the top to choose between 'Encode' or 'Decode' functions.

Paste a URL or raw text into the input box. Use the 'Batch' mode by putting one URL per line.

Choose 'Strictness' levels: 'Parameter' for data values or 'Full URL' for routable addresses.

Select 'Space Character' formatting: use '%20' for modern URLs or '+' for form-encoded data.

View the results instantly in the output area. Errors are highlighted with specific character positions.

When decoding, check the 'Query Parameters' table to view extracted keys and values in a grid.

Copy the result using 'One-Click Copy' or download the entire list as a .txt file.

Encoding Strictness Comparison

Symbol	Unencoded	Full URL (Loose)	Parameter (Strict)
Forward Slash	/	/	%2F
Question Mark	?	?	%3F
Ampersand	&	&	%26
Space	( )	%20	%20
Colon	:	:	%3A

Malformed URI Sequence Protection

A common failure point in URL decoding occurs when an input contains a rogue '%' sign followed by invalid characters. Standard JavaScript functions typically crash the entire page in this scenario. URL Encoder / Decoder includes built-in protection that catches these exceptions gracefully. If a malformed sequence is detected, URL Encoder / Decoder identifies the approximate character position and line number, allowing users to fix the string without losing their work. This ensures that URL Encoder / Decoder remains stable even when processing messy or corrupted logs.

Frequently Asked Questions

Is user data private when using URL Encoder / Decoder?

Yes. URL Encoder / Decoder runs 100% locally in the browser. No URLs or text data are ever sent to a server. Kilotoolkit is designed for total privacy.

What is percent-encoding?

Percent-encoding is the standard method for encoding information in a Uniform Resource Identifier (URI). It replaces non-ASCII characters and reserved symbols with a '%' followed by their two-digit hexadecimal value.

Can I encode a list of multiple URLs?

Yes. URL Encoder / Decoder supports batch processing. Simply paste multiple URLs into the input box with each one on a new line and the tool converts them all at once.

When should I use + instead of %20?

Use '+' if the data is being sent via an application/x-www-form-urlencoded header (like an old HTML form). Use '%20' for modern web development and RFC-compliant URL structures.

Why does the tool show a 'Malformed URI' error?

This occurs when the decoder finds a '%' character that isn't followed by two valid hex digits (0-9 or A-F). Check for accidental spaces or truncated strings at the end of the input.

Tool Layout Gallery

Interface and Features - URL Encoder / Decoder

What is the URL Encoder / Decoder? - URL Encoder / Decoder

How to Use the URL Formatter - URL Encoder / Decoder

Technical Specifications - URL Encoder / Decoder

Encoding Strictness Comparison - URL Encoder / Decoder

Malformed URI Sequence Protection - URL Encoder / Decoder

When to use this tool - URL Encoder / Decoder

Frequently Asked Questions about URL Encoder / Decoder - URL Encoder / Decoder

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