File Converters

Spreadsheets, CSV and JSON

CSV to JSON reads a CSV and returns an array of objects keyed by the header row — paste the text or drop the file, whichever is to hand. JSON to CSV, over with the developer tools, goes the other way and flattens nested objects into dotted column names.

CSV to Excel produces a real .xlsx workbook, which matters more than it sounds: renaming a CSV does not work, and opening one in Excel means an import dialogue that decides your product codes are numbers. A genuine workbook opens straight into Excel, Sheets and Numbers.

Excel to CSV is the return trip and is deliberately narrow: it takes the first sheet of an .xlsx or .xls workbook and writes the displayed cell values, so what you get is what the spreadsheet showed rather than the formulas underneath. If the data needs to end up as a printed table instead, CSV to PDF and Excel to PDF typeset it onto real pages with selectable text.

Audio and video

Video to Audio pulls the audio track out of an MP4, MOV or AVI and saves it as a 192 kbps stereo MP3 — the usual reason being a recorded talk, interview or lecture you want on a phone without carrying the picture. Audio Converter moves an existing audio file between MP3, WAV, Ogg Vorbis, FLAC and M4A, preserving the sample rate and channel count rather than quietly resampling.

Both run FFmpeg compiled to WebAssembly inside the page, which has a visible cost and a real benefit. The cost: the first conversion downloads the codec bundle, so the initial run is slow. The benefit: a two-gigabyte video is never uploaded, so there is no wait on your connection, no server-imposed size cap, and no copy of your footage anywhere.

Archives, and looking before you extract

ZIP Creator builds a ZIP from files on your machine — add and remove entries, name the archive, then pack at deflate level six, a middle setting that compresses well without a long wait.

ZIP Viewer is the more interesting half. It lists what is inside an archive with each entry's size by reading only the archive index: nothing is decompressed, nothing is written to disk and nothing is executed. That makes it the safe way to answer "what is actually in this attachment?" before you commit to extracting it.

Numbers, times and sizes

Timestamp Converter converts a Unix epoch timestamp into a readable date and back, with the current timestamp ticking live and an ISO 8601 form alongside — enough to settle most "is this seconds or milliseconds?" arguments at a glance.

Unit Converter covers four families and says so up front: length, weight, temperature and digital storage. There is no area, speed or currency conversion here, so you will not waste time hunting for a tab that is not there.

File Size Calculator takes one figure and shows it simultaneously in bytes, KB, MB, GB, TB and bits, on 1024-based units. It is a pure converter — there is no transfer-time estimate, because that would need a link speed it has no way to know.

Working with the files themselves

Batch File Renamer applies a find-and-replace, a prefix, a suffix and a counter across a list of files and shows you the resulting names before anything happens. Because a browser cannot rewrite your disk, it hands back renamed copies in a ZIP and leaves your originals exactly where they were — which is a limitation on paper and a safety net in practice.

File Metadata reports a file's name, MIME type, size, extension and last modified date without reading a single byte of its contents. A 60 GB video therefore reports as instantly as a text file. To read the metadata inside a file rather than around it, use Image Metadata for photographs or PDF Privacy Scanner for documents.

Producing something new

Three tools here generate a document rather than convert one. QR Generator turns a URL or any text into a QR code in your own colours and downloads it as a PNG; Wi-Fi and vCard codes work if you type the standard string yourself, as there is no wizard.

GST Invoice Generator produces an Indian GST tax invoice with the CGST/SGST or IGST split chosen automatically, HSN codes, rate-wise totals and the amount in words. POS Billing is a browser till: keep a product list, ring up a sale, apply a discount and print an 80 mm thermal or A4 receipt as a PDF. Both keep every figure on your own device.