Figure specs are published, numeric, and unforgiving in both directions. PLOS wants TIFF or EPS at 300-600 dpi, 789-2250 pixels wide at 300 dpi, 2625 pixels maximum height, and under 10 MB per file. Nature asks for 300-600 dpi for photographic images but caps supply at 300 ppi, because anything denser makes files too big for reviewers to download, and repeats the 10 MB ceiling. Springer splits by artwork type: photos and fine shading at 300 dpi minimum, halftone mixed with line art at 600 dpi, scans of line art at 1200 dpi. The trap is that the compression step most people reach for — re-saving a JPEG smaller — changes pixel dimensions and dpi metadata rather than just the byte count, and a figure that drops under 300 dpi at final printed size gets rejected at production, months after acceptance. The safe order is resize to the journal's column width in pixels first, then compress to land under the file cap, then convert to the required container. Skwish does the resize and compress steps in the browser with a per-file before/after readout, so you can see exactly which figures are still too heavy before you upload anything. Nothing leaves your machine.