Guides
Short answers to the questions people ask before they print: which size, how many pixels, which limits apply. Each guide names its sources and ends with the free check for your own image, which runs on your device.
Etsy printable sizes: the complete size guide for digital downloads
Which sizes to offer for an Etsy printable, the pixels each one needs, and the file limits Etsy states for digital listings.
Poster size in pixels: what resolution do you actually need?
Pixel dimensions for common poster sizes, how many pixels per inch to aim for, and what Printful and Printify say about resolution.