Amazon no-text lower-right rule vs Walmart contrast: where captions go

Amazon Sponsored Brands video ads forbid text in the lower right corner, and Walmart's rich media rules require 4.5:1 contrast for normal text, so burned-in captions for both need to sit higher in the frame and carry strong colors. Sume's caption endpoint lets you move the caption vertically and cap its width; it documents no horizontal alignment control, so check one still of the result before a batch.

What each platform says

Amazon's Sponsored Brands video specs page (read 2026-10-08) lists 6 to 45 seconds, 16:9 only, no letterboxing and no text in the lower right corner. Walmart's Rich media: Technical requirements PDF (last updated Sep 17, 2026, read 2026-10-08) sets AA contrast of 4.5:1 for normal text and 3:1 for text larger than 18 px, with logos exempt.

What Sume's caption call can move

POST /v1/video-captions burns text and returns a captioned video. Its placement object has anchor_ratio and landscape_anchor_ratio, which set the vertical position, and typography.safe_width_ratio, which limits how wide the text can run. design.colors takes base, active, stroke, accent, accent_deep and card, where a null card shows no card.

Raising the anchor ratio lifts the caption off the bottom edge, which is where the Amazon corner sits. A narrower safe width keeps lines off the right edge. A caption job is a flat $0.20 for videos up to 60 seconds.

Check before the batch

Neither platform publishes a pass or fail test for a finished file, and Sume does not report contrast. Burn the caption onto one clip, pull a still with POST /v1/video-frames at the time the caption is on screen, and look at where the text lands and how it reads against the background.

If the line still reaches the lower right, move the anchor up again, or use a card color so the text keeps its contrast. Run the whole set only after one still passes.

Amazon's 6 to 45 second window also leaves room for a longer caption track than a 15-second clip. If the clip is 30 seconds with speech throughout, the caption stays on screen most of the time, so the lower right is occupied for longer and the placement test matters more.

Keep the test cheap: one caption job on a 10-second cut costs $0.20, and one frame pull is a small Modal compute charge plus a platform fee. That is far less than a rejected ad.

• The two rules are independent; a high-contrast caption can still break Amazon's corner rule.
• Walmart also asks for plain language and no flashing; those are not caption settings.
• A caption job is $0.20 per video up to 60 seconds, so redoing one still costs $0.20.