+ kitlumo

New: File Converter

Convert files locally — including Word and Excel.

Images, whole PDFs, Word DOCX, Excel XLSX, text, code, CSV and JSON stay on your device. KitLumo never receives or stores a copy.

PDF · Word · Excel · Images

Free online utilities

Free online developer tools.

Straightforward tools that work right here on your phone, tablet or computer. No account, no AI, no nonsense.

Your tool data stays on this device. Anything you type, paste, calculate or open in a tool is not sent to us. KitLumo does not receive it or save a copy.
141 free tools Browser-first No account

KitLumo Developer tools

Use developer tools as checks, not blind deployment

Developer tools can format JSON, encode values, inspect URLs, compare text and prepare small snippets. They help you see structure and catch obvious mistakes, but the application or service that receives the output remains the final test.

Never paste production passwords, private keys, access tokens or customer data into a general-purpose utility. Use a representative sample and verify the result in the target environment.

Browse all developer tools Read the privacy notice

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Practical guides

Understand the result, not just the number.

Short, plain-language guides explain the assumptions, privacy and limits behind the most important KitLumo tools.

View all guides
PDF to WordWhat text reflow preserves PDF to ExcelHow pages become worksheets Mortgage paymentsWhat the estimate includes Percentage changeWhich formula answers the question Unit conversionHow to check measurements Calculator checklistHow to check a result

Available now

Useful from the first click

27 tools

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Developer

JSON Formatter

Format, validate or minify JSON in one place.

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New

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CSV to JSON

Turn comma-separated data into clean, copyable JSON.

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64
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Base64 Converter

Encode or decode text without sending it anywhere.

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%20
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URL Encoder

Encode or decode URL text safely in your browser.

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ID
New

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UUID Generator

Generate random UUIDs for software and data work.

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@
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Timestamp Converter

Convert Unix timestamps to readable dates and back.

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JWT
New

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JWT Decoder

Inspect a token’s header and payload locally. No verification.

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JSON to CSV

Turn a JSON array into a tidy, spreadsheet-ready CSV file.

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URL
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URL Parser

Break a URL into its host, path, query values and more.

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HTML Entities

Encode or decode HTML entities without sending text anywhere.

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Number Base Converter

Convert integers between binary, octal, decimal and hexadecimal.

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Regex Tester

Test a regular expression and inspect every match safely.

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MB
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Data Size Converter

Convert between bytes, KB, MB, GB and their binary equivalents.

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CSS
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CSS Clamp Calculator

Build a responsive CSS clamp value for fluid sizes.

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A→Z
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JSON Key Sorter

Sort object keys recursively for stable, readable JSON.

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64▧
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Image to Base64

Convert a local image to a data URL without uploading it.

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XML Formatter

Indent compact XML so it is easier to inspect and edit.

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CSS
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CSS Minifier

Remove comments and extra whitespace from stylesheet code.

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404
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HTTP Status Lookup

Look up the plain-English meaning of common HTTP codes.

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/24
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Subnet Calculator

Calculate an IPv4 network, mask, broadcast address and host count.

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Text to HTML

Escape plain text safely for use in HTML markup.

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HTML
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HTML to Text

Remove HTML markup and recover readable plain text.

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CSV
New

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CSV Column Picker

Extract one named column from local CSV data.

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.*
New

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Regex Escape Tool

Escape special characters for an exact regular-expression match.

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?=
New

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URL Query Builder

Build a URL with safely encoded query parameters.

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MIME
New

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MIME Type Lookup

Find the usual content type for common file extensions.

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SVG
New

Developer

SVG to Data URI

Turn SVG markup into a data URI for CSS or HTML.

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Tool workspace

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Help shape KitLumo

Don’t see what you need?

Tell us the task you are trying to solve. The most-requested tools guide what we build next.

How KitLumo stays free

Supported by ads. Helped by people.

Clearly labelled ads fund the website so everyone can use every tool for free. If KitLumo saves you time, you are also welcome to make an optional donation to help pay for hosting and keep the tools available.

Donating never unlocks extra features. Every tool remains free for everyone.
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How it works

Free means free.

KitLumo is built around small, focused utilities. No login walls, no artificial limits and no AI layer where a reliable tool will do.

Every tool currently available works directly on the phone, tablet or computer you are using. Anything you type, paste, calculate or open in a tool is not sent to us, and KitLumo does not save a copy.

Your saved and recently used tool shortcuts are stored only in your browser on this device. When you use “Report a problem” or “Request a free tool,” only that message and any email address you choose to add are sent to KitLumo.

Help shape KitLumo

Request a tool