QUICK ANSWERStart with the tool that matches your immediate input.
Open Sepia Photo Effect first when its stated purpose matches the result you need now. Use Stitch Images Horizontally only when it solves a separate next task.
This guide is for creators, marketers, designers, and website owners. Start with Sepia Photo Effect when your immediate task is to use the Sepia Photo Effect to complete this file task privately in your browser. Move to Stitch Images Horizontally only when you also need to use the Stitch Images Horizontally 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 Stitch Images Horizontally solves a genuinely different next step.
Both tools sit in Image & Design, but they handle different inputs or outcomes. Keeping those roles separate reduces repeated work and makes verification easier.