Pre-flight checks that run in your browser

These tools tell you what is actually in a file before you import or convert it. Everything runs inside your own browser; no file is sent to a server.

Three ground rules

Nothing is uploaded. The file you select is read by the page alone, and no external API is called. Open your browser developer tools on the Network tab before you run a check and you can confirm it yourself.
Your original file is left alone. The CSV inspector reports leading zeros and formula candidates without correcting them. The image tool writes its result as a new file and never touches the one you selected.
Nothing is guessed. You choose the CSV encoding, and bytes that cannot be read that way stop the check rather than becoming replacement characters. An image is identified by reading its own header, so a file that is not really a PNG, JPEG or WebP is named and refused.

Available now

CSV inspector

Check how a CSV file is actually structured before you import it into Excel or another system. You choose the encoding and the separator; the tool reports rows and columns, rows whose column count differs, quoting that breaks the CSV rules, leading zeros and values a spreadsheet may read as a formula. The same values can then be saved as UTF-8 CSV.

Decode as UTF-8 or Shift_JIS by your choice; bytes that cannot be read are reported, never replaced
Switch between comma, tab and semicolon separators to see how the same file splits
Leading zeros, formula candidates and date-like values are listed without being rewritten
The limit is 2,097,152 bytes (2 MiB). A larger file is refused rather than partly read

Open the CSV inspector → Import UTF-8 CSV in Excel without garbled characters Related practical guides

Image resizer and converter

Change the pixel size of an image and save it as PNG, JPEG or WebP. The aspect ratio is always preserved. JPEG cannot store transparency, so you choose the colour that fills transparent areas. After converting, the format that was actually produced and the measured size change — smaller or larger — are shown. The file on your computer is not modified.

The container is identified by reading the start of the file itself, not by trusting the name or MIME type
Animated WebP and animated PNG (APNG) are refused and named, never reduced to a first frame
A format this browser cannot encode is disabled rather than silently replaced by PNG
The limit is 20,971,520 bytes (20 MiB) and 40 megapixels; each output edge is capped at 12,000 px

Open the image tool → PNG, JPEG and WebP compared Related practical guides

This is the complete list. Anything still being built is added here only once it actually works.

Where the guides take over

These tools stop at inspecting or converting the file in front of you. Which setting to choose, the Excel import steps and the application settings behind them are covered in the practical guides.

Apps and practical guides →