To get an image below an upload limit, first check the required format, maximum bytes and minimum pixel dimensions. Then export from an unchanged original and adjust one variable at a time. A smaller file is only acceptable if it still meets the receiving form rules and preserves the information the image is meant to show.
Identify which limit is failing
A file-size limit in KB or MB is different from a pixel-dimension limit. Some forms also require an aspect ratio or reject formats they cannot decode. Read the specific error before changing the image. A renamed extension does not change its contents, and changing DPI metadata alone does not reduce the pixel data.
Try quality before crossing minimum dimensions
For a photographic JPEG, create a moderately lower-quality candidate from the original and inspect the important detail. Keep the dimensions fixed at first so you can see whether quality alone is enough. For text or diagrams, compare an appropriate lossless format rather than forcing JPEG to meet the byte target at the expense of readability.
Reduce dimensions when the rules allow it
Illustrative example: a form requires a JPEG under 500 KB and at least 800 pixels wide. If a 2400-pixel source remains too large, try 1600 pixels, compare the result, then consider another reduction while staying above the minimum. Those numbers describe a hypothetical form, not a universal preset.
Measure the actual file bytes after each export. If the application interprets KB differently, leave a small margin under the stated limit rather than targeting the boundary exactly.
Check the file you submit
Open the final export, confirm its actual format, inspect small text and check that orientation is correct. Submit that copy rather than an older file with a similar name. If the original is already very small or the required detail cannot survive further reduction, ask the receiving service for an accepted alternative instead of repeatedly recompressing the same lossy copy.