Why is part of my line grey when there is no comment there?
The tokenizer treats the first // or # on a line as the start of a comment and greys out everything after it. A URL inside a string, a CSS hex color, or a Python f-string with a hash will all trip this. Switch the syntax tint to Off if the mis-colouring is worse than plain text.
What resolution is the exported PNG?
The canvas is drawn at 2x device scale, so the file is twice the on-screen dimensions in both directions. The width follows your longest line of code plus the window and outer padding, and the height follows the line count at 26 pixels per line, so the exact pixel size changes with your snippet.
Can I use my own theme or brand color for the background?
No. There are six preset gradients (Indigo, Sunset, Ocean, Forest, Slate, Candy) and one fixed dark window at #0d1117 in a GitHub-dark-style palette. If you need a brand background, export the PNG and composite it in your design tool.
Does my code get uploaded to make the image?
No. The image is drawn on an HTML canvas inside your tab and exported with canvas.toBlob, so the snippet never leaves your machine. That matters if you are screenshotting code that contains internal names, keys, or unreleased work.
Why does the image look so wide?
The window is sized to fit your longest line without wrapping. A single long line, such as a minified import or a long string literal, stretches the whole canvas. Break the line, trim the snippet, or accept an image that will be scaled down to illegibility in most feeds.
Are tabs preserved?
No. Every tab character is replaced with two spaces before rendering, so a tab-indented file will render with a narrower indent than you see in your editor. Convert to your preferred space width in the textarea first if the indentation matters.