QUICK ANSWERStart with the tool that matches your immediate input.
Open File Type Identifier first when its stated purpose matches the result you need now. Use Markdown Preview only when it solves a separate next task.
This guide is for writers, office teams, students, and data workers. Start with File Type Identifier when your immediate task is to use the File Type Identifier to complete this file task privately in your browser. Move to Markdown Preview only when you also need to use the Markdown Preview to complete this file task privately in your browser.
The goal is not to run two tools automatically. It is to finish the first narrow task, inspect its result, and then decide whether Markdown Preview solves a genuinely different next step.
Both tools sit in Documents & Files, but they handle different inputs or outcomes. Keeping those roles separate reduces repeated work and makes verification easier.