Colors · 4 min read
One color. A code for every place.
Convert colors between HEX, RGB, HSL, OKLCH and wide-gamut formats in your browser. Keep opacity, understand gamut changes and copy a useful code without uploading anything.
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A little know-how.
A lot less guesswork.
Plain guides to smaller PDFs, lighter images, clearer data, and the small choices that make everyday file jobs easier.
Colors · 4 min read
Colors that leave the words clear.
Check text and background colors against WCAG contrast thresholds, including transparency. Find a passing text color and preview approximate color vision differences locally.
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Colors · 4 min read
From one swatch to a useful palette.
Build color harmonies and tonal scales, extract a palette from a local image, mix colors and make CSS gradients. Export CSS, JSON, design tokens, SVG or PNG from your browser.
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Colors · 4 min read
A brand color, with its source beside it.
Browse sourced company color palettes, copy HEX codes and CSS variables, or explore their contrast. See the scope of each reference, from published brand guides to logo samples.
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A little know-how · 5 min read
Under the limit, and still worth watching.
Make a video fit under 25, 10 or 8 MB in your browser: how the bitrate, frame rate and size are chosen, and how close the result looks. No uploads.
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A little know-how · 5 min read
Any video, in the format you need.
Convert video to MP4, WebM, MOV or MKV in your browser: when it is copied and when it is encoded, which format and quality to choose. Nothing is uploaded.
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A little know-how · 4 min read
From MOV, WebM or MKV to an MP4 that plays everywhere.
Turn iPhone MOVs, WebM screen recordings and MKV files into MP4s that play everywhere, copied as they are when they can be, in your browser. No uploads.
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A little know-how · 4 min read
Keep the part that matters. Lose nothing else.
Cut an MP4, MOV, WebM or MKV to the part you want in your browser: copied without encoding, or exact to the frame. Cut out parts, split into files and save frames. No uploads.
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A little know-how · 3 min read
Every picture, in the shape it is shown.
Crop a video to 9:16 for Reels, Shorts and TikTok, to a square or to 4:5, in your browser, many at once. Nothing is uploaded.
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A little know-how · 3 min read
Faster or slower, and still in tune.
Change a video's speed from half to twice as fast in your browser, the sound stretched so its pitch stays the same. Nothing is uploaded.
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A little know-how · 2 min read
The picture, without a sound.
Take the audio out of MP4, MOV, WebM and MKV videos in your browser, the picture copied as it is so nothing is lost. Nothing is uploaded.
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A little know-how · 3 min read
Every video, as loud as the next.
Set a video's sound to −14, −16 or −23 LUFS in your browser, measured by BS.1770 as streaming services and broadcasters measure it, its peaks held under −1 dBTP. The picture is not touched.
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A little know-how · 3 min read
The right sound under every picture.
Put music or a voice-over under a video in your browser: in place of its sound or mixed under it, looped to fit and faded at the end. Nothing is uploaded.
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A little know-how · 3 min read
A title on the picture, a mark in the corner.
Write a title or caption on a video and put a logo in a corner in your browser, for the whole video or a few seconds. Nothing is uploaded.
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A little know-how · 3 min read
The moment, on a loop.
Turn a moment of an MP4, MOV or WebM into a GIF, animated WebP or APNG in your browser: trim it, crop it, caption it, choose the size. Nothing is uploaded.
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A little know-how · 3 min read
Many clips, one video.
Join MP4, MOV, WebM or MKV clips end to end in your browser, in the order you choose: copied without encoding when they match, the sound in step. Nothing is uploaded.
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A little know-how · 3 min read
Words on the picture, in every player.
Burn the subtitles from an SRT or WebVTT file into a video in your browser, so they show on every site and player. They follow any trim or speed change. Nothing is uploaded.
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A little know-how · 6 min read
Write in plain text. Read it as a page.
Write Markdown with a live preview in your browser: GitHub's tables, task lists, footnotes and alerts, maths, diagrams, tabs, a document check and exports to HTML, Word and PDF. No uploads.
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A little know-how · 3 min read
From Markdown to a page anyone can open.
Convert Markdown to HTML in your browser: one web page with its look inside it, or the HTML alone, with GitHub's tables, code, maths and diagrams. Cleaned so nothing in it runs.
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A little know-how · 3 min read
Markdown, set for paper.
Turn Markdown into a PDF from your browser's print dialog, laid out for paper: headings kept with their text, tables and code not cut in half. No uploads, no account.
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A little know-how · 4 min read
Markdown into Word, headings and all.
Turn Markdown into a Word file with Word's own heading styles, numbered lists, tables, links, pictures and footnotes, in your browser. Nothing is uploaded.
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A little know-how · 3 min read
Any web page, as clean Markdown.
Turn HTML files, web pages and copied text into clean Markdown in your browser: headings, lists, links, tables and code blocks, written as GitHub writes them.
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A little know-how · 3 min read
Word files, written as Markdown.
Turn .docx files into Markdown in your browser: headings, lists, tables, links, bold and italic, with their pictures kept. Nothing is uploaded.
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A little know-how · 3 min read
Tables without counting pipes.
Make Markdown tables in a grid of cells or by pasting from Excel or Google Sheets, then line up their pipes and add rows and columns in place. Free, in your browser.
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Start here · 5 min read
Eleven free tools that never ask for your files.
Every KeepSimp tool: edit, compress, merge and split PDFs, resize and convert images, convert GIFs and audio, format JSON and pick colors. Free, no sign-up, your files stay with you.
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Images · 4 min read
A lighter image, without the upload.
How to compress an image in your browser, choose useful settings, and compare the result before replacing your original.
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Images · 5 min read
The right size, without losing the important part.
How to resize an image in your browser: by pixels or percent, in cm or inches for print, for social posts and websites, one image or fifty at once. Free and nothing is uploaded.
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A little know-how · 4 min read
JPEG, PNG or WebP? Pick the right fit.
A practical guide to choosing an image format for photos, transparent graphics and everyday browser sharing.
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GIF, WebP, APNG or video? Choose how it moves.
A practical guide to choosing a format for an animation: where it will play, what it shows, and how large the file may be.
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A little know-how · 6 min read
One PDF from many, without the upload.
How to merge PDF files in your browser: put them in order, arrange single pages, keep links and bookmarks, and decide what a merge should carry over.
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A little know-how · 6 min read
Just the pages you need, without the upload.
How to split a PDF in your browser: cut it where you can see, at bookmarks, by size or at blank pages, and get parts that are no larger than they should be.
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A little know-how · 7 min read
A smaller PDF, with its words still sharp.
How to make a PDF smaller in your browser: find out what makes it big, shrink its pictures without blurring its text, reach a size limit, and handle scans properly.
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A little know-how · 4 min read
Under 200 KB, and still easy to read.
How to compress a PDF to 100 KB, 200 KB, 500 KB or 1 MB for a job, visa or exam form. Name the size and get the best quality that fits, free, in your browser, with nothing uploaded.
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A little know-how · 5 min read
Write on a PDF, without sending it anywhere.
How to add text, pictures, shapes and drawings to a PDF in your browser: fill a form that has no fields, mark a page, and download a file that was checked. Free, with nothing uploaded.
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A little know-how · 4 min read
Mark it up, and keep it to yourself.
How to highlight, underline and strike out text in a PDF, add notes and reply to comments in your browser, and download real comments or a clean final copy. Free, nothing uploaded.
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A little know-how · 4 min read
Sign it, and keep it to yourself.
How to sign a PDF in your browser: draw, type or photograph your signature, place it, fill in the blanks and the date, and download. Free, with no account and nothing uploaded.
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A little know-how · 4 min read
Fill it in, and send only what you mean to.
How to fill in a PDF form in your browser: type into its fields, tick boxes, choose from lists, sign and download, as a form or made final. Free, with no account and nothing uploaded.
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A little know-how · 4 min read
Trim the page, and know what trimming means.
How to crop a PDF in your browser: drag a frame or type the numbers, for one page or all, or make pages A4 or Letter size. And why a cropped page still holds what was cut off. Free, no upload.
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A little know-how · 4 min read
Number the pages, where you want the numbers.
How to add page numbers to a PDF in your browser: choose how they are written and where, skip the cover, add a header, a footer or Bates numbers. Free, with no account and nothing uploaded.
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A little know-how · 3 min read
Mark it as a draft, without sending it anywhere.
How to add a watermark to a PDF in your browser: DRAFT, Confidential or a logo, as faint and as large as you like, on all pages or some. And what a watermark does not do. Free, no upload.
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A little know-how · 4 min read
A black box is not a redaction.
How to redact a PDF in your browser so that names, numbers and pictures are removed from the file, not covered. Why a black box fails, how to check, and what else a file gives away.
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A little know-how · 3 min read
Make a form people can fill in.
Turn a PDF into a form with text fields, checkboxes, radio groups, lists and dates. Move, resize and name its fields on your device, without uploading the file.
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A little know-how · 4 min read
A scan you can search.
How to make a scanned PDF searchable in your browser: its words are recognised on your device and laid unseen over the pages, which look the same. What OCR misreads, and how to check.
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A little know-how · 4 min read
Is the signature still good?
Check the digital signatures in a PDF in your browser: whether each still holds, whose certificate made it, and what was added to the file after it was signed. Nothing is uploaded.
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A little know-how · 4 min read
A new format, with nothing lost on the way.
Convert audio between MP3, M4A, Opus, FLAC and WAV in your browser, many files at once, with tags and cover art. Which format and bitrate to choose. Nothing is uploaded.
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A little know-how · 3 min read
Keep the sound, leave the picture.
Take the sound out of an MP4, MOV, WebM or MKV video in your browser, exactly as it is, or as MP3, M4A, FLAC or WAV. Nothing is uploaded.
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A little know-how · 4 min read
Just the part you want, with no click at the cut.
Cut a song, a voice note or a podcast to the part you want, to the millisecond, with fades in and out, in your browser. Every edit can be undone. Nothing is uploaded.
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A little know-how · 3 min read
Your song, when the phone rings.
Make an iPhone ringtone (M4R, up to 40 seconds) or an Android ringtone (MP3) from any song in your browser, faded at the end, and put it on your phone. Nothing is uploaded.
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A little know-how · 5 min read
Every file as loud as the next.
What LUFS and true peak are, which loudness to choose for Spotify, podcasts or broadcast, and how to normalize many audio files at once in your browser, without clipping. Nothing is uploaded.
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A little know-how · 3 min read
Louder, without the crackle.
Make a quiet recording, song or video's sound louder in your browser. Why turning it up can make it crackle, and how a limiter stops that. Nothing is uploaded.
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A little know-how · 3 min read
One long recording, in parts you can find.
Split a long recording, podcast, lecture or mix into parts in your browser: every few minutes, into equal parts, at markers or at its pauses. Nothing is uploaded.
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A little know-how · 3 min read
Many recordings, one file, no jumps between.
Join MP3, M4A, WAV and other sound files into one in your browser, in your order, straight on, with silence or crossfades, with chapters. Nothing is uploaded.
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A little know-how · 4 min read
Faster or slower, the notes where they were.
Change the speed of a recording, song or podcast without changing its pitch, or the pitch without changing its length, in your browser. Also tape speed, reverse and karaoke. Nothing is uploaded.
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A little know-how · 4 min read
The words kept, the noise left behind.
Take hiss, fans, traffic, mains hum, clicks and harsh "s" sounds out of voice recordings in your browser, with RNNoise running on your device. Nothing is uploaded.
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A little know-how · 4 min read
The right name on every song, the sound left alone.
Change the title, artist, album, track number, lyrics and cover of MP3, M4A, FLAC, Ogg, Opus and WAV files in your browser, many at once, without encoding the sound again. Nothing is uploaded.
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A little know-how · 4 min read
Press record, keep every sample.
Record from a microphone in your browser, with pause and a level meter and no call filters unless you want them, then trim, clean up and save it as MP3, M4A or WAV. Nothing is uploaded.
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A little know-how · 4 min read
Every word written down, none of it sent away.
Turn speech in a recording, interview or video into text and subtitles with Whisper running in your browser, then search it and play along. Nothing is uploaded.
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A little know-how · 3 min read
A sound, a picture, and a waveform that moves.
Turn a song, podcast clip or voice note into an MP4 with its cover or a picture of your own, a moving waveform and its title, in your browser, to share where only video goes. Nothing is uploaded.
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A little know-how · 3 min read
Ask your agent, and the work stays on your computer.
Give Claude Code, Codex or an agent in your browser KeepSimp's tools: they run in a hidden browser on your computer, read your files where they are and save results beside them.
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A little know-how · 6 min read
Give your agent the chores. Keep your files at home.
Batches, chains of jobs and design-system checks: how to have Claude Code or Codex do file chores with KeepSimp's tools, on your own computer.
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A little know-how · 4 min read
Why a converted MP3 starts late, and ours does not.
MP3 and AAC encoders add a few hundredths of a second of silence to every file. Why it happens, when it matters (loops, albums, ringtones), and how files can say how long their sound really is.
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Developer notes · 4 min read
Make JSON readable. Keep the details.
Format and minify JSON locally while preserving large numbers, escaped strings and the order of your keys.
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Developer notes · 4 min read
Find the JSON you need with JSONPath and Pointer.
Query nested JSON with JSONPath, select an exact value with JSON Pointer, and export results without rounding large IDs.
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Developer notes · 4 min read
Repair, compare and patch JSON with a preview.
Review JSON repairs, compare values instead of whitespace, and generate or apply all six JSON Patch operations locally.
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Developer notes · 4 min read
Check your JSON against a schema, locally.
Validate JSON Schema draft-07, 2019-09 and 2020-12, inspect error paths, use local references, and infer a starting schema.
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Developer notes · 5 min read
Take JSON into YAML, CSV, JSON Lines and TypeScript.
Convert JSON locally, keep CSV identifiers as strings, review spreadsheet formula protection, and generate sample types and schemas.
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