30 free tools · no sign-up · no uploads

Small tools, properly made.

Zento Tools is a workbench of thirty single-purpose online tools — generators, converters, " "checkers, calculators and counters. Every one of them runs entirely in your browser, so nothing " "you type, paste or open ever leaves your device.

30free tools
6categories
0accounts or uploads
100%client-side

Security

Passwords, hashes and IDs — lock things down properly.

SecurityPassword GeneratorRandom passwords with a live strength readout, made on your device. SecurityPassphrase GeneratorMemorable word-based passphrases with honest strength scoring. SecurityPassword Strength CheckerGrade any password: entropy, crack time and weak-pattern alerts. SecurityHash GeneratorMD5, SHA-1 and SHA-2 fingerprints of any text, computed locally. SecurityUUID GeneratorVersion-4 UUIDs in bulk — true random, copy or download.

Images

Compress, resize, convert and favicon-ify without uploads.

ImagesImage CompressorShrink JPG, PNG and WebP photos right in the browser. ImagesImage ResizerExact pixel dimensions for any image — ratio lock included. ImagesImage ConverterPNG, JPEG and WebP — genuinely re-encoded, every direction. ImagesFavicon GeneratorFour real favicon sizes from any image — or just a letter.

Colour

Pickers, palettes, gradients and contrast ratios.

ColourPalette GeneratorHarmonious five-colour palettes from any starting colour. ColourGradient GeneratorBuild smooth CSS gradients with a live preview and one-click code. ColourContrast CheckerExact WCAG contrast ratios for any text and background pairing. ColourColour StudioOne colour, four formats — HEX, RGB, HSL, HSV — with copy buttons.

Data

JSON, Base64 and URL encoding — developer staples.

DataJSON FormatterFormat, validate and minify JSON with honest error messages. DataJSON to CSV ConverterConvert JSON arrays to CSV spreadsheets — and back — correctly. DataBase64 Encoder & DecoderEncode and decode Base64 with proper UTF-8 — emoji-safe, always. DataURL Encoder & DecoderPercent-encode URLs and components — or decode them — live. DataRegex TesterTest regular expressions with live highlighting.

Text

Count, convert, compare and generate placeholder text.

TextDiff CheckerSpot every change between two versions of a text, line by line. TextWord CounterLive word, character and time stats for any text you paste. TextCase ConverterRestyle text in 13 cases — UPPER to camelCase — in one click. TextLorem Ipsum GeneratorPlaceholder text by paragraph, sentence or exact word count. TextMarkdown PreviewerWrite Markdown, see formatted output live. TextText to SpeechHear any text read aloud in your browser.

Calculators

Everyday maths: BMI, age, units and percentages.

CalculatorsBMI CalculatorBody mass index with healthy-range guidance, metric or imperial. CalculatorsAge CalculatorExact age from any birth date, plus totals and next birthday. CalculatorsUnit ConverterLength, weight and temperature converted live as you type. CalculatorsPercentage CalculatorDiscounts, tips and change — every common percentage case. CalculatorsStopwatch & TimerPrecision stopwatch with laps, plus a countdown timer. CalculatorsRandom Number GeneratorFair random numbers, dice rolls and coin flips.

Why another tools site?

Because most of them treat the tool as bait. The real product is usually the sign-up form, the file you upload, or the data trail you leave behind. Zento Tools is built the other way round: the tool is the product. You arrive, you do the job, you leave — and since every calculation happens inside your browser, there is no server quietly keeping a copy of what you made.

Built like a tool, not a funnel

Each page follows one template: the working tool at the top, then a plain-language explanation of what it does, its honest limits, and answers to the questions people actually ask. No countdown timers, no fake download buttons, no maze of ads between you and the result. If a tool cannot do something, the page says so.

Latest articles

ArticleRegular Expressions Without Fear: A Plain-English GuideRegex looks like keyboard static, but ten tokens cover almost everything. Learn them with plain examples and useful patterns. ArticleMarkdown in 10 Minutes: Write Once, Publish EverywhereHeadings, lists, links, code and tables — the plain-text format behind READMEs, docs and notes apps, learned in minutes. ArticleHow Text-to-Speech Actually WorksFrom plain text to spoken waveform: normalization, phonemes, prosody, and how neural voices learned to sound human. ArticleRandomness: Why Computers Are Bad at It and How They Fake ItComputers are deterministic machines, so true randomness must be stolen from physics. How PRNGs, entropy pools and crypto APIs work. ArticleThe Pomodoro Technique and Why Timers Make You FocusTwenty-five minutes on, five off: the timeboxing method, the psychology behind it, and the mistakes that kill it.

Frequently asked questions

Are the tools really free?

Yes. Every tool on this site is free, with no account, no quota and no watermark on anything you download or copy.

Is anything I type or open uploaded?

No. All processing happens in your browser with JavaScript. There is no upload endpoint for the tools to send your data to — you can verify it by loading a tool, disconnecting from the internet, and watching it keep working.

Do the tools work offline?

Once a page has loaded, yes. The calculations are local, so a dropped connection does not stop the work.

Why does every tool live on its own page?

So each page can explain its tool properly and load fast, and so you can bookmark exactly the tool you use every week.

Can I suggest a new tool?

Yes — the contact page is the place. The collection grows by request, and gaps are listed honestly rather than filled with half-finished tools.