How to use it

1. Open Spreadsheet Converter.
2. Drag a spreadsheet file onto the drop zone, or click to select one.
3. Choose the output format from the buttons (XLSX, XLS, ODS, CSV, JSON, HTML).
4. Click Convert — the file processes in your browser.
5. Click DOWNLOAD in the bottom bar to save the converted file.

Use cases

• Turning a CSV export from an old system into JSON for an API.
• Opening an ODS file from a colleague who does not use Excel.
• Converting a small table into an HTML snippet for a documentation page.

PRIVACY — Unlike AI tools that require uploading files to a server, this runs entirely in your browser. Your data never leaves your device.

How to use it

1. Open Converter → Document Converter.
2. Load a DOCX, ODT, TXT, or HTML file via upload or drag-and-drop.
3. Read the preview to see what the converter actually found inside it.
4. Pick the output format (DOCX, TXT, HTML) and save, keeping the original in case the conversion loses formatting.

Use cases

• Reading an ODT file when only Office is installed on your machine.
• Checking what is actually inside a DOCX before converting it.
• Turning a plain-text export back into a readable HTML page.

Limitation — Files are processed locally in your browser. Nothing is uploaded.

How to use it

1. Open Converter → Media Converter.
2. Choose a video or audio file. Large files take longer because the work happens on your device.
3. Select the output format and any codec options.
4. Run the conversion and download the result, then play it to confirm it is not corrupted.

Use cases

• Converting a MOV from a phone into MP4 that a site will play.
• Extracting audio from a video for a podcast clip.
• Changing a container without re-encoding when the codec is already supported.

Limitation — Files are processed locally in your browser. Nothing is uploaded.

How to use it

1. Open Converter → Text Format Converter.
2. Paste Markdown, HTML, or LaTeX into the source box, or drop a .md, .html, or .tex file on the upload bar above it. The cap is 2 MB, and the extension sets the source format for you.
3. Choose the source and target format from the two rows of chips: MD, HTML, and LaTeX. The same format on both sides keeps the Convert button disabled; the swap button flips both formats and the two boxes together.
4. Press the Convert button, whose label names the target format (Convert to HTML, for example), or use Ctrl+Enter — Cmd+Enter on a Mac. Pandoc is a WebAssembly download, so the first conversion takes longer than the ones after it.
5. Copy the result with the copy icon, or press DOWNLOAD in the bottom bar. HTML comes out as a standalone document, and the downloaded file takes the name of the file you loaded.

Use cases

• Writing a README in Markdown and checking the rendered HTML.
• Converting a LaTeX citation block to something a web page accepts.
• Turning a LaTeX snippet into HTML for a blog post.

Limitation — Text only: .md, .html, and .tex up to 2 MB, pasted or dropped. A plain .txt file is read using whichever source format is currently selected. Word, PDF, and image files are refused here, and Pandoc has to rewrite structure the target format cannot carry, so tables, footnotes, and styling can change shape.

How to use it

1. Open Converter → Spreadsheet to PDF.
2. Drop an .xls, .xlsx, .ods, .csv, .json, or .html file on the upload box — 20 MB maximum, and an HTML file has to contain a <table>.
3. If the workbook has more than one sheet, choose the one to include.
4. Press Create PDF. The table is drawn on A4 portrait with 10 mm margins and split across pages when it runs past one.
5. Press DOWNLOAD in the bottom bar to save it — the file takes the name of the spreadsheet you loaded, with a .pdf extension.

Use cases

• Sending a clean copy of figures you do not want edited by the recipient.
• Printing a table that has lost its cell borders in a copy-paste.
• Attaching a readable version of a sheet to an email thread.

Limitation — Reads .xls, .xlsx, .ods, .csv, .json, and HTML files up to 20 MB, one sheet per PDF. The PDF is a rasterised image of the table, so its text cannot be selected or searched, and there are no landscape, paper-size, or margin controls.

How to use it

1. Open Converter → Split Files.
2. Choose the file to split; the cap is 500 MB.
3. Set the chunk size in MB. Parts are numbered -part-001, -part-002, and so on.
4. Press Split file. The parts and a manifest.json are packed into one ZIP.
5. Press DOWNLOAD in the bottom bar, and keep the manifest together with the parts.

Use cases

• Sending a large export through an email or chat size limit.
• Handing a long log or backup to someone who needs it in parts.
• Testing what a pipeline does when a file arrives in pieces.

Limitation — Parts are streamed per chunk, but the ZIP is assembled in memory before download, so a file near the 500 MB cap depends on the tab’s free memory. No encryption or password; manifest.json only records names and order.

How to use it

1. Open Converter → Join Files.
2. Choose the parts, in any order. Leave manifest.json out of the selection.
3. Keep "Sort by name" on when the parts carry -part-001 numbering, or turn it off to keep your own order.
4. Press Join files.
5. Press DOWNLOAD in the bottom bar. The name comes from the first part with its -part-NNN suffix removed.

Use cases

• Restoring a file that was split with this tool, using its manifest as the order.
• Combining byte-split archives received over several messages.
• Checking that a split-and-join round trip returns the original bytes.

Limitation — Concatenates raw parts in name order or the order you picked. It does not read manifest.json, compute a checksum, or repair anything — the wrong order gives a broken file of the right size.

How to use it

1. Open Converter → Corrupt File.
2. Choose the file to damage; the cap is 50 MB.
3. Set the percentage of bytes to change, and keep the first 1 KB intact if the header should survive.
4. Press Corrupt file.
5. Press DOWNLOAD in the bottom bar to save the -corrupted copy. The file you picked is not modified.

Use cases

• Checking that an upload validator rejects a truncated or damaged file.
• Testing backup and recovery procedures against a realistically broken file.
• Reproducing a “cannot open this file” bug without damaging the original.

Limitation — Random overwrite only, capped at 50 MB. It cannot target a specific structure, it does not record which bytes changed, and the damage cannot be undone — work on a copy.