You are entering the Diversity Visa programme and the form refuses your photo. The size limit is the part a tool can fix; the shape, pixels and photo rules are the parts you have to get right first. This page lists all of them, from the instructions, so you know which problem you actually have.

What the requirements say

Who needs 240 KB

These verified limits are at or just above 240 KB.

What each of these limits covers

US Diversity Visa (DV) entry photo: Digital photo upload. The DV instructions require a JPEG of 240 kB or less, in a square aspect ratio, 600 x 600 pixels. Read on a US Embassy site's copy of the State Department's DV-2026 instructions, because travel.state.gov itself was blocked. The 'kB' is read as decimal, the smaller reading. Check the current year's instructions before each DV entry period. Source: cm.usembassy.gov

Tips at 240 KB

Crop to a square and resize to the required pixels before compressing. A correctly sized photo is usually far under the limit already, so the size problem often disappears.
Save as a JPEG, not HEIC, PNG or WEBP, because the requirement names the format.
Check the current year's instructions. The requirements here are read from the DV-2026 instructions, and they can change between entry periods.

Requirement	What it says	Read on
File format	JPEG (.jpg)	cm.usembassy.gov
Maximum file size	240 KB or less	cm.usembassy.gov
Shape	Square: height equals width	cm.usembassy.gov
Dimensions	600 x 600 pixels	cm.usembassy.gov
Scanning an existing photo	2 x 2 inches (51 x 51 mm), scanned at 300 pixels per inch	cm.usembassy.gov
Eyeglasses	Not allowed	cm.usembassy.gov