Frequently Asked Questions

No. Not a single byte. All file processing happens entirely in your browser using JavaScript. When you upload a file or paste data, it is loaded into your browser's memory and processed locally — it is never sent to any server, database, or third-party service.

You can disconnect from the internet after the page loads and all tools will continue to work perfectly. That's how local it is.

We don't use any tracking cookies, analytics scripts, or fingerprinting. We don't know who you are, where you're from, or what you converted. We literally have no backend to log this information to.

The only external requests the page makes are to load fonts from Google Fonts and libraries from Cloudflare's CDN — standard stuff that every website uses, and neither of these can see your files.

Yes — because nothing leaves your device. Your CSV, Excel, notebook, or PDF is processed entirely in your browser's memory. Once you close the tab, it's gone. There's no cloud storage, no server logs, no database.

This is especially important for PDF Studio — salary slips, government forms, contracts, and signed documents are processed locally and never transmitted anywhere. For the most sensitive data, you can download Muffin and run it locally with no internet connection at all.

Go to Muffin's PDF Studio and click the Fill & Sign tab. Upload your PDF, then drag on any blank field to draw a text box over it. Type your text inside. Use the toolbar to choose font (Helvetica, Times Roman, or Courier), size (8–32), and color (black, blue, red, green, or custom). Drag the handle bar at the top of the box to move it, drag the corner to resize. Download when done — your PDF never leaves your browser.

Go to the Signature tab in PDF Studio. Two options:

• Draw it — use your mouse or touchscreen to draw your signature on the canvas. Adjust pen color and thickness.
• Upload a photo — take a photo of your handwritten signature on white paper and upload it. Muffin automatically removes the white background using pixel brightness detection, leaving only the ink as a transparent PNG.

Click Save as PNG to download your extracted signature — so you don't have to re-draw it every time you need to sign a document. Then load your PDF, click once anywhere to place the signature, drag it to the right spot, and resize by dragging the corner. Double-click on an empty area for a confirmation prompt before placing.

In the Fill & Sign tab, the toolbar has three modes:

• T Text box — drag to draw a box and type inside it
• ✓ Tick mark — click anywhere to stamp a checkmark. Useful for marking checkboxes on forms, indicating approval, or annotating options
• S̶ Strikethrough — drag horizontally to draw a line through text or a field. Useful for crossing out incorrect entries or indicating deletion

All three can be moved by dragging, resized by dragging the corner handle, and deleted by hovering and clicking ×. All are embedded into the downloaded PDF.

Go to the Crop PDF tab in PDF Studio. Upload your PDF, then drag on the page to draw a rectangle around the area you want to keep — the area outside turns dark so you can see exactly what will be removed. Click Apply crop and choose to apply it to the current page only or all pages at once. Download your cropped PDF.

This is useful for removing large blank margins from scanned documents, stripping headers or footers, or trimming a PDF to a specific region before sharing.

Most popular online PDF editors require account creation and upload your file to their cloud servers. That means your salary slips, academic documents, government forms, and signed contracts are stored on someone else's infrastructure.

Muffin's PDF Studio processes everything locally in your browser using PDF-lib and PDF.js — the same open-source libraries used in production by major software projects. Close the browser tab and there is no trace of your document anywhere. No account, no upload, no storage.

The visualizer accepts any standard flat CSV or Excel (.xlsx) file where the first row is a header row and each column has a name. It works best when your data is structured like this:

It does not support multi-row headers (like merged cells in Excel where one header spans multiple columns). If your Excel file has that, flatten it to a single header row first.

Yes — fully supported. The Y Axis shows checkboxes for every column. Just tick the ones you want — no Ctrl+click needed — and they all appear as separate neon-colored lines with a legend. There is also a toggle all link to select or deselect everything at once.

Colors used: purple, green, pink, yellow, light blue, orange, red — always visible on the dark background. Try the 🤖 5 Models F1 Score sample dataset to see this instantly.

Four chart types are supported:

• Line chart — best for training curves, trends over time
• Bar chart — best for comparing values across categories or models
• Scatter plot — best for correlations between two variables
• Histogram — best for seeing the distribution of a single column

You can also enable Highlight best value to mark the maximum or minimum point on any line with a star marker.

Yes — click the PNG button above the chart to download it as a high-resolution 1200×700px PNG image, ready to drop into a paper, report, or presentation.

In Google Colab: go to File → Download → Download .ipynb. Then upload that file to Muffin's Notebook Cleaner. It strips all outputs, resets execution counts, and removes Colab metadata — same result as running nbstripout, but no Python or terminal needed.

For most use cases — especially pushing to GitHub — check all three of these:

• Remove cell outputs — clears all printed output, images, tables, error messages
• Reset execution counts — resets the In[N] counters to null so diffs are clean
• Strip notebook metadata — removes kernel info and Colab-specific metadata

If you're seeing an error like "the 'state' key is missing from metadata.widgets" on GitHub or nbviewer, also check Remove widget state — this removes the broken widget metadata that causes that error.

Yes. At the top of the Notebook Cleaner page you'll see two tabs — Single Notebook and Batch Clean. Click Batch Clean, drop multiple .ipynb files at once, and all of them get cleaned with the same settings in one go. Each notebook gets its own download link showing how many outputs were removed and how much smaller the file got.

This is useful if you have a full folder of experiment notebooks you want to clean before pushing to GitHub — for example before submitting a research project or doing a final commit before publication.

Three reasons: size (notebooks with outputs can be 100MB+), diffs (every run changes timestamps and execution counts making PRs unreadable), and privacy (outputs can accidentally contain API keys, file paths, or sensitive data you don't want public).

Cleaning before every commit is considered best practice. Tools like nbstripout do this automatically — Muffin's cleaner does the same thing on demand, in your browser.

Go to Muffin's Image & PDF Converter and click the Merge PDFs tab. Drop your PDF files, reorder them with the ↑↓ arrows if needed, give your output a filename, and click Merge PDFs. Download button appears instantly.

Yes, completely. Muffin uses PDF-lib to copy pages directly from each PDF into the merged file. The text, images, fonts, and layout are preserved exactly — nothing is re-rendered or compressed. The output is identical to the originals, just combined.

No hard limit — you can merge as many PDFs as you want. The only practical limit is your browser's memory. Very large PDFs (100MB+ each) may be slow, but for typical lecture slides, research papers, or reports it will be fast.

The merging happens entirely in your browser, so no file is uploaded anywhere.

Yes — use the Images to PDF tab in the same tool. Drop multiple PNG, JPG, or WebP images and each one becomes a page in the PDF, in upload order. You can reorder with arrows before creating. Choose A4, Letter, or fit-to-image page size.

The Data Converter supports: CSV, JSON, JSONL (newline-delimited JSON), and Excel (.xlsx). You can convert between any combination — CSV → JSON, JSON → CSV, Excel → CSV, CSV → JSONL, JSONL → JSON, Excel → JSON, and so on.

Yes. Switch to Select columns to keep mode at the top of the converter. Load your file and checkboxes appear for every column. Uncheck the ones you don't need and only the selected columns appear in the output.

This is useful when your Excel or CSV has many columns — like model name, epoch, accuracy, F1, precision, recall, inference time — but you only need a subset for a specific analysis or report. Use Check all / Uncheck all buttons to quickly select or deselect everything.

Really, genuinely free. No freemium tier, no file size limit behind a paywall, no "export to CSV requires Pro". The tools are just HTML, CSS, and JavaScript — they cost virtually nothing to host.

We're two people who built this in our spare time because we needed these tools ourselves. No VC funding, no team of 40. Just two people who got tired of sketchy upload-your-file websites.

The best ways to support Muffin:

• ☕ Sponsor our coffee — If Muffin saved you an hour of work, consider buying us a coffee. (Ko-fi link coming soon!)
• 🔗 Connect on LinkedIn — Say hi to Sneha Chakraborty or Divyansh Pathak. It genuinely makes our day.
• 📢 Share it — Tell a colleague, post it in your team Slack, mention it in a paper footnote. Word of mouth is how small tools grow.
• 🐛 Report bugs — If something breaks, reach out on LinkedIn. We actually fix things.

We're open to it! Muffin is built for data scientists and researchers — if your product is relevant to that audience, reach out on LinkedIn. We'd rather work with sponsors whose tools we'd actually use ourselves.

We'll never show intrusive ads or partner with anything spammy. Any sponsorship will be tasteful and clearly labelled.

Send a message on LinkedIn — Sneha Chakraborty or Divyansh Pathak. We read every message and take bug reports seriously. Feature requests that come up repeatedly actually get built.