60 free tools · everything runs locally
Everyday tools that never upload your files
Merge PDFs, work out a mortgage, compare two drafts, convert a spreadsheet or find a meeting time across time zones. Every tool runs inside this page, and each one explains exactly how it gets its answer.
The file stays on your device
- 60
- tools
- 8
- in-depth guides
- 0
- bytes uploaded
- 2
- languages
Most used
What most people come here to do.
All 60 tools
Grouped into nine kinds of job. Every tool page explains how to use it, how it works and when its answer can be wrong.
PDF tools
5 tools · Merge, split, reorder and convert PDF pages
- Merge PDFCombine several PDFs into one, choosing pages and order. Files never leave your device.
- Split PDFSplit a PDF into several files, or pull out just the pages you need.
- PDF to imageTurn PDF pages into PNG or JPG images at the resolution you need.
- Organize PDFReorder, rotate and delete PDF pages visually, then save a new file.
- Images to PDFCombine JPG, PNG and other images into one PDF, the right way up, without uploading them.
Calculators
9 tools · Loans, interest, dates and percentages, with the working shown
- Mortgage calculatorMonthly payment, total interest and a full amortization schedule, with extra payments.
- Compound interest calculatorGrowth of savings with regular contributions, at any compounding frequency.
- Date calculatorDays between dates, business days, adding days or months, and exact age.
- Percentage calculatorPercent of a number, percentage change, increases, discounts and reverse percentages.
- BMI calculatorBody mass index in metric or imperial units, with WHO and Chinese categories and a healthy weight range.
- BMR & calorie calculatorBasal metabolic rate by Mifflin-St Jeor, and daily energy needs by activity level.
- Pregnancy due date calculatorEstimate the due date and how many weeks pregnant you are, from the last period or conception.
- China retirement age calculatorFind the statutory retirement age and date under China's gradual retirement-age increase from 2025.
- Child height percentile & growth chartPlot a child's height on WHO, US CDC or Chinese growth charts and estimate adult height.
Money & tax
7 tools · Take-home pay, income tax, VAT and the true cost of borrowing
- True APR calculatorFind the real annual rate of an instalment plan, flat-rate loan or fee-based offer.
- VAT & GST calculatorAdd or remove VAT, GST or sales tax, with official rates for 13 countries.
- China take-home pay calculator (social insurance and housing fund)Net monthly salary in China after social insurance, housing fund and income tax, with Beijing and Shanghai 2026 contribution bases.
- China income tax calculator (salary and bonus)Monthly Chinese individual income tax and take-home pay under cumulative withholding, and the best way to tax an annual bonus.
- UK take-home pay calculatorSalary after Income Tax, National Insurance, student loan and pension for the 2026 to 2027 tax year, including Scotland.
- US paycheck calculator (federal)Take-home pay after 2026 federal income tax, Social Security, Medicare and 401(k), per paycheck and per year.
- Tip calculator & bill splitterWork out the tip and split the bill evenly, to the cent or rounded up.
Text tools
6 tools · Count, compare, clean up and re-case text
- Word counterWords, characters, sentences and reading time — correct for mixed English and Chinese.
- Case converterUPPER, lower, Title and Sentence case, plus camelCase, snake_case and more.
- Text compareSee exactly what changed between two versions of a text, line by line and word by word.
- Sort & dedupe linesSort lines alphabetically or naturally, remove duplicates and empty lines.
- Markdown to HTML converterTurn Markdown into clean HTML or a ready-to-open .html file, or into styled rich text for WeChat articles.
- Find and replaceFind and replace text with plain matching or regular expressions, with a live preview.
Developer tools
12 tools · Token counter, redaction, JSON repair, regex, cron and SQL formatting
- JSON formatter and repairPretty-print, minify and validate JSON with exact error positions, and repair the broken JSON that AI models produce.
- LLM API pricing comparisonCompare API prices for GPT, Claude, Gemini, DeepSeek, Qwen, Kimi and GLM in one table and see what each request costs.
- Token counter & AI cost calculatorCount tokens, estimate API cost and check context-window fit in your browser, with exact and approximate numbers kept apart.
- Redact sensitive data before AIReplace API keys, tokens, passwords, emails and phone numbers in logs and configs with placeholders, then restore them in the AI's reply.
- Regex testerLive match highlighting, capture groups, a replace preview and a plain-English explanation of each part of the pattern.
- JSON to TypeScript interfaceTurn a JSON response into TypeScript interfaces or a Zod schema, merging array items and marking optional fields.
- Cron expression translatorTranslate a cron expression into plain English, list its next run times in any time zone, and catch the day-of-month / day-of-week trap.
- SQL formatterTurn one-line SQL into clean, readable formatting for MySQL, PostgreSQL, SQL Server, Oracle and a dozen other dialects.
- Base64 encoder & decoderEncode and decode Base64 for text and files, including URL-safe Base64.
- Unix timestamp converterConvert Unix time in seconds, milliseconds or nanoseconds to dates and back.
- URL encoder & decoderPercent-encode or decode URLs and query values, and split a URL into its parts.
- JWT decoderRead a JSON Web Token's header, payload and expiry — without sending it anywhere.
Data & spreadsheet tools
4 tools · Convert between CSV, JSON, Excel and Markdown tables
- YAML ⇄ JSON converterConvert YAML to JSON and back, and flag values like no, 0755 and 22:22 that different parsers read differently.
- CSV ⇄ JSON converterConvert CSV to JSON and back, with correct quoting, delimiters and encodings.
- Excel to CSVExport any sheet of an .xlsx file as CSV or JSON, with dates converted correctly.
- Markdown table generatorBuild or paste a table and get neatly aligned Markdown for GitHub and wikis.
Unit & number converters
7 tools · Units of measurement, number bases and Roman numerals
- Chinese ID number checkerValidate a Chinese resident ID number's check digit and read the date of birth, age, sex and issuing region, in bulk and offline.
- Unit converterLength, weight, temperature, area, volume and speed, using exact definitions.
- Number base converterBinary, octal, decimal, hex and any base to 36 — with two's complement and float bits.
- Subnet calculator (CIDR)Enter an IP with a prefix or mask to get the network and broadcast addresses, usable host range, masks and address type, and split subnets.
- Roman numeral converterConvert numbers to Roman numerals and back, with strict checking of the rules.
- Number to wordsWrite numbers and amounts out in English words, cheque style, or as Chinese financial numerals.
- Color converter & contrast checkerConvert between HEX, RGB and HSL, and check text contrast against WCAG.
Time & productivity
6 tools · Time zones, countdowns and a focus timer
- Time zone converterSee one moment in several cities and find meeting hours that work for everyone.
- Countdown timerCount down to a date or for a set time, with an alarm and a shareable link.
- Pomodoro timerFocus and break cycles with adjustable lengths and a daily count.
- Chinese lunar calendar converterConvert between the Chinese lunar and Gregorian calendars, find a lunar birthday in any year, and look up the 24 solar terms (1901–2099).
- China working days calculatorCount working days in mainland China, or find the date N working days ahead, with public holidays and make-up workdays.
- StopwatchAn online stopwatch with laps, keyboard shortcuts and CSV export that stays accurate in background tabs.
Random & security tools
4 tools · Passwords, random picks and file hashes
- Password generatorStrong random passwords and passphrases, with an honest strength estimate.
- Random name pickerSpin a wheel, draw names, shuffle a list or split people into fair teams.
- MD5 & SHA hash generatorMD5, SHA-1 and SHA-2 checksums for text and files, with automatic comparison.
- UUID generatorGenerate random v4 or time-ordered v7 UUIDs in bulk, and inspect any UUID.
Privacy
Why local processing matters
The documents people most often need to process are the ones they least want to share: contracts, pay slips, scanned IDs, customer exports, API tokens. A typical online tool uploads the file, processes it on a server you know nothing about and sends back the result. For the jobs on this site that detour is unnecessary. A current browser can rewrite a PDF, parse a spreadsheet, hash a gigabyte file and convert time zones on its own, so that is where the work happens.
Local processing has practical benefits too. Nothing waits in an upload queue, so large files are limited by your device rather than by a server's size cap. Tools keep working on a train or a plane once the page has loaded. And there is no account, no daily limit and no watermark, because there is no server-side cost to ration.
Check it yourself
You do not have to take the claim on trust. In Chrome, Edge or Firefox press F12 (on a Mac, Option-Command-I), open the Network tab and then use any tool — merge two PDFs, paste a JSON file, generate a password. You will see the page load its own scripts and, where enabled, the advertising and analytics scripts described in the privacy policy. You will not see a request that carries your file or your text.
For an even stricter test, load a tool, switch your computer to airplane mode and use it. Everything except the ads keeps working.
What every tool page includes
- How to use it, step by step, written against the actual controls on the page.
- How it works: the formula, standard or algorithm behind the result, with links to the primary source — RFCs, NIST, IANA and the like.
- Worked examples whose numbers are computed by the tool's own code and checked by automated tests before every release.
- Limits: the situations in which the result can be wrong or surprising, stated plainly.
Guides
A tool answers one question; a real task usually needs several. These guides take one task at a time and work it through.
- 01PDF toolsPrepare a PDF for an upload portalTurn a pile of scans and documents into one clean PDF that an application portal will accept.
- 02CalculatorsPrepay the mortgage or invest?How to compare paying down a loan with investing the same money — with the numbers worked out.
- 03Text toolsWhy word counts disagreeWord, Google Docs and online counters give different numbers. Here is why, and which to trust.
- 04Developer toolsDebugging an API responseA walk through four common API problems: broken JSON, rounded IDs, expired tokens and wrong timestamps.
- 05Data & spreadsheet toolsCSV and Excel pitfallsWhy CSV files come out garbled, lose leading zeros or turn into dates in Excel — and how to move data safely.
- 06Unit & number convertersUnits in recipes and travelCups, ounces, Fahrenheit, miles and gallons: the conversions you meet in the kitchen and abroad, and where they trip people up.
- 07Time & productivityScheduling across time zonesFind a meeting time that works in several cities, survive the daylight saving weeks, and write deadlines nobody can misread.
- 08Random & security toolsPasswords that lastWhat makes a password strong, what current guidance says about length and forced changes, and where hashes and fair draws fit in.