HTML5 banners: what a ZIP check can catch before upload

An HTML5 banner can open on a designer’s laptop and still fail after upload. The local machine may supply files that were left out of the ZIP, tolerate a path difference, or bypass the destination platform’s click handling.

Preflight checks reduce avoidable upload failures. They do not replace testing inside the environment where the creative will run.

Start with the package structure

Identify the intended entry HTML file and confirm that the required local assets are present. Look for references to images, scripts, fonts, and stylesheets outside the package.

Keep filenames and references consistent, including capitalization. A reference to “Logo.png” may not resolve to “logo.png” in every hosting environment.

Ask the receiving platform for its current packaging requirements. Google’s HTML5 asset preparation guide describes ZIP and clickTag expectations for Campaign Manager 360. Those requirements should not be copied blindly into a specification for another platform.

Separate declared size from actual rendering

The creative may declare a 300 × 250 size while rendering elements outside that area. A static size check can identify the declaration; a visual check is needed to inspect the result.

Test the beginning, intermediate frames, and end state. Look for clipped text, hidden controls, missing fonts, or a final frame that becomes blank after the animation ends.

For a set of assets, use the bulk creative asset checker to inventory files. A directory with ten ZIPs is not automatically a complete ten-size delivery.

Inspect the click behavior

A variable named clickTag is useful evidence, but its presence alone does not prove that every intended clickable area uses it correctly.

Confirm the required variable name and implementation with the platform. Check whether the banner opens the approved destination through the supported mechanism, and whether a hard-coded URL bypasses the configured destination.

For multiple exits, document which region leads where. Do not assume a one-exit checker can validate a more complex interactive experience.

Review external dependencies

A package can reference resources outside the ZIP. Establish whether those requests are permitted, whether they use secure URLs, and what happens if they fail.

An external font or library may work during testing but introduce an availability dependency. Treat that as a production consideration rather than a reason to copy arbitrary code into the package.

The HTML5 banner checker can inspect a ZIP for supported preparation issues without executing the creative. Its findings should be read as errors or warnings about the checks performed, not a platform-approval certificate.

Finish with a platform preview

Upload the approved version, allow any required review to complete, and test rendering and clicks in the destination preview. Confirm the final asset ID against the handoff.

Save the source ZIP, the checked version, findings, and approval reference together. If the creative is replaced, repeat the checks on the replacement rather than transferring approval from the old file.

A short preflight record makes the next upload faster because it shows what was checked and where runtime behavior still needed confirmation.