Guides

What happens to a file you upload, what a document reveals about you, and which format to choose. Written to answer the question, not to sell an upgrade.

• Is it safe to upload documents to an online converter?Usually, but not always, and you cannot verify it. Uploading sends a complete copy of your document to a company’s servers, where retention, staff access and breach exposure are governed by their policy rather than by anything you control.
• What your PDF is telling people, and how to checkA PDF usually carries your name, the software you used, creation and modification times, and sometimes GPS coordinates from embedded photos. Black boxes drawn over text almost never delete it — the words remain selectable underneath.
• PNG, JPG or WebP — which should you actually use?Use JPG for photographs, PNG for logos, diagrams and anything needing transparency, and WebP when you want either of those roughly a third smaller. The deciding question is whether the image has hard edges or smooth gradients.
• Why did my file get bigger after converting it?Almost always because the new format is a poor fit for that content — a photograph saved as PNG, or an already-compressed image re-saved losslessly. Compression is not a property of the file; it is a bet about what the content looks like.
• How do you actually reduce a PDF’s file size?Almost all PDF bulk is embedded images, so shrinking their pixel dimensions is the fix that works. Removing pages, fonts or metadata saves far less than people expect, and re-compressing already-compressed scans usually degrades quality for almost nothing.
• What does a photo reveal about you?A phone photo usually records GPS coordinates accurate to a few metres, the exact date and time, the device model and its serial-adjacent identifiers. Anyone who receives the original file can read all of it in seconds, without special tools.
• Why does my JSON say invalid when it looks fine?Almost always a trailing comma, single quotes, an unquoted key or a comment. JSON is far stricter than JavaScript object syntax, and every one of those is legal in a JavaScript file and illegal in a JSON document.
• The unit conversions people get wrong, and whyThe three big ones: applying a linear factor to an area or volume, treating feet-and-inches or stone-and-pounds as decimals, and converting a temperature difference as though it were a temperature. Each is a systematic error, not a rounding one.