Detection From the Bytes
Signatures identify workbooks, images, PDFs and media; CSV, JSON, YAML and Markdown are recognised by structure. Confidence is reported, so the page can say "probably CSV" instead of asserting it.
File Converter
Spreadsheets, data, text, audio and video in your browser
Drop a file and see what it can honestly become
Web Tool
Official product page
Publisher:
POLPROG
Official product page
13
Formats read
4
Media targets
7
Direct routes
0
Bytes uploaded
01 / File Converter
About
Most converters ask you to pick both ends of a conversion before you start, which assumes you already know which format you have. Often you do not: a .txt that is really a semicolon-separated export and a .json that is really YAML are both common. So this tool takes the file first, identifies it from its bytes, and shows the extension beside the detected format when the two disagree - rather than quietly overruling you.
It converts between CSV, TSV, JSON, YAML, XML, Markdown, HTML, plain text and Excel workbooks, reading and writing .xlsx with the browser's own decompression rather than a megabyte of library.
Audio and video are converted here too, and still nothing is uploaded. A WebAssembly build of FFmpeg is downloaded once - about 8 MB, only when you actually pick a media conversion - and runs in a worker on your machine. MP4 uses H.264 with AAC, WebM uses VP8 with Vorbis, and MP3 or WAV can be pulled out of anything with sound. It runs on a single core, so the page estimates the wait before you commit, shows FFmpeg's own progress while it works, and lets you stop it.
What it will not do matters as much. Image and PDF conversions are links to the Image Toolkit and the PDF Toolkit, not a second weaker engine. PDF to Word is not offered at all, because a faithful one needs layout reconstruction a browser cannot do. VP9 is not offered because it crashes in this build. Every conversion that loses something says so before you download the result.
02 / Use case
What it solves
The problem
- A file with the wrong extension gets converted as the wrong format and comes out as one column of noise.
- Converting a spreadsheet or a video means uploading it to a site with an unread privacy policy.
- Converters offer conversions they cannot really do, and the result only falls apart later.
The outcome
- The format is read from the content, and the mismatch with the name is shown rather than hidden.
- Documents, spreadsheets, audio and video all convert on your own device.
- Conversions that would lose something say so first, and the ones that cannot be done well are not offered.
Who it is for
- Anyone with a spreadsheet, an export or a recording and a privacy policy to respect.
- Developers moving data between CSV, JSON, YAML and XML.
- People who need an MP3 out of a video without installing anything.
03 / Key Features
Key Features
The most important capabilities, explained in practical terms.
Spreadsheets Both Ways
Reads .xlsx with the browser's own DecompressionStream and writes it back with numbers as numbers and leading-zero codes kept as text, so identifiers survive the round trip.
Structured Data
CSV, TSV, JSON, YAML and XML in every direction that makes sense. Nested values are either flattened into dotted columns or reported by path - never silently dropped.
Markdown and HTML
Markdown to HTML and back, and either to plain text. Raw HTML inside Markdown is escaped rather than passed through, because this runs on files from strangers.
Audio and Video, On Your Device
FFmpeg in WebAssembly, downloaded once and only when needed. MP4 (H.264 and AAC), WebM (VP8 and Vorbis), MP3 and WAV, with a real progress readout and a cancel button.
Delegation Instead of Duplication
Images go to the Image Toolkit, PDFs to the PDF Toolkit and JSON editing to the JSON Formatter. Those rows are links, marked as leaving, not buttons pretending to a second implementation.
Seven Direct Routes
CSV to XLSX, CSV to JSON, JSON to CSV, JSON to YAML, YAML to JSON, Markdown to HTML and HTML to Markdown each have their own page with that conversion already chosen.
Legacy character encodings
A CSV out of a Polish or Czech Excel is not UTF-8. The encoding is worked out from the bytes - UTF-8, Windows-1250, ISO-8859-2, Windows-1252, ISO-8859-1 and the UTF-16 that Excel writes for "Unicode text" - and can be set by hand when the guess is wrong.
Columns under your control
Choose which columns go out, rename them and reorder them before the file is written. The preview follows every edit, so what is on screen is what the download contains.
What a conversion drops
Nesting flattened into dotted columns, YAML comments, formulas reduced to their last value, every sheet but the first: each conversion states what it cannot carry across before you run it, not after.
04 / Download
Product access
A clear path from the official source to your first successful workflow.
Choose the right platform
Use one of the official links available for your device or browser.
Install or open
Follow the store instructions or open the web application. No third-party installers.
Configure and begin
Review the options, choose your preferences and start with the core workflow.
Official access options
05 / Technology
Technology behind the product
A transparent look at the core technologies used to build and maintain this product.
JavaScript
06 / Security
Privacy & Security
Your data stays on your device. Always.