fastmod is a fast partial replacement for codemod. Like codemod, it is a tool to assist you with large-scale codebase refactors, and it supports most of codemod's options. fastmod's major philosophical difference from codemod is that it is focused on improving the use case "I want to use interactive mode to make sure my regex is correct, and then I want to apply the regex everywhere". For this use case, it offers much better performance than codemod. Accordingly, fastmod does not support codemod's --start, --end, or --count options, nor does it support anything like codemod's Python API. For each match of the regex, you'll be shown a colored diff and asked if you want to accept the change (the replacement of the <font> tag with a <span> tag), reject it, or edit the line in question in your $EDITOR of choice.