HTML5 banner ads: specs, sizes and what breaks

IAB standard sizes

The Interactive Advertising Bureau defines the display sizes most platforms accept. Google Ads, Display & Video 360 and Campaign Manager 360 all build on this list. The widths and heights below are the pixels the creative must render at; the zip you deliver can contain multiple sizes.

• All sizes are width x height in pixels.
• Platforms may support a subset; always confirm the target platform's current list before building.
• Responsive or "fluid" sizes are not part of the IAB fixed list and need separate handling.

Source: IAB Display Advertising Guidelines and Google Ads Help (HTML5 ad specifications), as of October 2026.

Animation limits and file weight

Every platform caps the total animation time and the delivered file size. Exceed either and the creative is rejected or served as a static backup.

• Animation length: 30 seconds maximum, including all loops. After 30 seconds the animation must stop on the final frame.
• Frame rate: 24 fps recommended; higher rates increase file size without visual benefit.
• Total file weight (zip): 150 KB for most Google Ads placements; 200 KB for Display & Video 360; Campaign Manager 360 allows up to 2.2 MB for rich media but standard HTML5 stays at 200 KB.
• Initial load: The first frame must render within the weight budget before any polite load starts.
• Polite load: Additional assets (video, large images) may load after the page signals it is ready; they count toward the total weight.

Backup image and clickTag

HTML5 creatives require a static fallback and a standardised click handler.

1. Backup image (JPG or PNG): One per HTML5 size, same pixel dimensions, under 40 KB for the 300 x 250 size (scale proportionally for others). The backup shows when the browser cannot run the HTML5 or when the ad is paused.
2. clickTag variable: The creative must read the click-through URL from a global clickTag (or clickTAG) variable supplied by the ad server. Do not hardcode the destination URL in the creative.
3. ExitApi (Google Ads): For Google Ads, call ExitApi.exit() on click; the creative must not open a window directly.
4. Naming: Include the size in the backup filename (for example backup_300x250.jpg) so the trafficker can match it without opening every file.

Common rejection reasons

When an HTML5 zip is rejected, the error usually falls into one of these buckets.

• Zip over the weight limit: Unminified JS, embedded fonts, or video pushed into the initial load.
• Missing or wrong clickTag: Hardcoded URL, typo in the variable name, or no click handler at all.
• Animation runs past 30 seconds: Infinite loop or a loop count that exceeds the time cap.
• Backup image missing or wrong size: No fallback, or the backup dimensions do not match the HTML5 canvas.
• Insecure assets: HTTP references inside the zip (images, fonts, scripts). All assets must be HTTPS or relative.
• Expandable or floating behaviour not declared: Creatives that resize, expand or break the iframe need the appropriate creative type flag in the ad server.
• Auto-play video with sound: Video must be muted by default; sound only on user interaction.