Effective web banners fit the placement, load without unnecessary delay, communicate an offer and its qualifications clearly, respect the reader’s control, and are measured for viewability—not just delivery. Start with the current IAB New Ad Portfolio, then verify the destination publisher’s exact requirements: no single set of dimensions, formats, or animation rules applies everywhere.
Start with the placement, not an old size chart
Before designing a banner, identify where it will run and obtain that publisher’s current creative specifications. Confirm the accepted formats, dimensions or aspect ratios, file-size limits, animation rules, and submission or implementation requirements. Specifications can differ even between placements offered by the same publisher, and a creative accepted on one site may be rejected on another.
Use the IAB Tech Lab’s New Ad Portfolio as a general starting point. Its newer guidance uses flexible units, aspect ratios, and size ranges rather than relying only on fixed desktop and mobile pixel dimensions. That approach is better suited to responsive layouts, but it does not override a publisher’s own requirements. The portfolio page was last updated February 7, 2024; check the current guidance and the placement’s own documentation before delivery.
- Record each placement and its specifications before you build assets.
- Ask whether a placement expects a particular aspect ratio, a range of sizes, or separate creative files for different contexts.
- Confirm how the creative will be served and previewed, including any ad-operations handoff or validation process.
- Recheck requirements when a campaign moves to a new publisher, placement, or device context.
Apple News illustrates why this matters: Apple documents its own accepted image formats, minimum asset dimensions, file-size limits, and animation restrictions. Its banner rules are for Apple News, not a universal standard. In particular, Apple’s documented limit of no more than three GIF loops and 15 seconds total applies to that placement; it should not be applied to unrelated sites unless their specifications say so.
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A banner has little room to explain an offer, so use a clear hierarchy: the main benefit or offer first, a direct call to action second, and only the supporting detail needed to understand the claim. A viewer should not have to infer what is being offered or where a click will lead. Keep text legible at the actual display size and check the creative at the smallest responsive rendering it is expected to support.
Keep claims and qualifications together
In the United States, the Federal Trade Commission’s small-business guidance says that advertising disclosures must be “clear and conspicuous.” If a qualification is needed to prevent a claim from misleading a consumer, place it near the claim, use plain language, and make it readable rather than tiny, buried, or visually overwhelmed. FTC staff guidance also emphasizes that disclosures should work on the devices and platforms where the ad appears.
For example, a prominent offer should not depend on a remote landing-page footnote to reveal an important limitation. Review the whole impression: headline, imagery, offer, qualification, and call to action together. Check whether the meaning changes when the creative is reduced, cropped, or displayed on another device. These are U.S.-specific legal guidance points; they are not a summary of the law in every jurisdiction. Advertisers should check requirements applicable to their markets and claims.
Build for a light, responsive experience
The IAB New Ad Portfolio emphasizes lightweight, encrypted, AdChoices-supported, and non-invasive advertising. Its experience principles are Respect, Control, and Choice: the reader’s primary task is consuming publisher content, and the reader should retain control over the advertising experience. Apply those principles to both the asset and how it behaves in the page.
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- Keep the initial creative lean. Include only the assets and code needed to show the message promptly. Avoid loading optional work before the first display if it is not needed to render the banner.
- Use responsive planning. Check that the visual hierarchy survives the aspect ratios and size range specified for the placement. Do not assume that simply shrinking one fixed layout will preserve readability.
- Avoid disruptive behavior. Do not make the ad interfere with the reader’s content task or remove meaningful control over the experience.
- Follow the placement’s technical limits. File budgets, supported formats, and animation behavior are publisher-specific; the platform’s acceptance criteria take precedence over a general design preference.
HTML5 banners should be treated as small web projects, not just exported pictures. They can include HTML, JavaScript, CSS, SVG, and media. The way those assets are organized and packaged affects how quickly the creative appears. The IAB’s HTML5 advertising guidance covers generating and packaging assets, testing the result, and coordinating with ad operations before a live campaign. Test the complete package through the same operational route planned for launch, rather than relying only on a local preview.
Test the creative before launch
A review should cover both visual behavior and delivery. Use the publisher’s preview or ad-operations workflow to check the submitted creative in its intended placement. A screenshot of a page can help a team review what is visible at a particular viewport, but it does not establish that the ad will be served, accepted, or viewable in a live campaign.
- Verify the package. Confirm that the required files and formats are present, the creative stays within the publisher’s limits, and its assets are packaged as expected.
- Check responsive states. Review the aspect ratios or size range in the specification. Look for clipped text, illegible qualifications, crowded calls to action, and imagery that loses meaning.
- Review the full claim. Confirm that necessary qualifications remain close to the claim and are legible in each tested presentation.
- Check the experience. Ensure the ad does not disrupt content consumption or remove user control.
- Use the campaign’s actual delivery workflow. Confirm the creative with ad operations or the publisher before launch, and resolve any validation or acceptance issues there.
- Capture useful QA records. Save the placement, viewport or preview context, creative version, and review date with the team’s notes so that a visual check can be repeated after a change.
For a quick visual record of a public preview page or landing page, ScreenshotNeo can return a screenshot from one GET request. This is a supplementary visual check, not a replacement for publisher preview tools or live ad-delivery testing. In particular, a capture of a page cannot prove that an impression was served or that a reader had an opportunity to see the ad.
Or skip the browser setup
To capture a public preview URL without setting up a browser automation stack, make one API request. The example saves a WebP screenshot; replace the target URL with your preview or landing-page URL. See the ScreenshotNeo API documentation for request options.
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpScreenshotNeo removes cookie/consent banners, newsletter popups, and chat widgets before capture; each of those steps can be turned off. Bot checks/CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and responses identify the page verdict and billing status. Its MCP server offers take_screenshot, get_page_info, and capture_pdf for Claude, Cursor, or another MCP client. The Free plan includes 1,000 shots per month with no card; paid plans start at $5 for 3,000 shots. If a consent notice or other removable widget is part of the experience you specifically need to inspect, turn off the relevant removal step for that capture. Sign up for 1,000 free screenshots a month, with no card required.
Measure viewability separately from delivery
A served impression confirms delivery under the ad system’s reporting rules; it does not prove that a person had an opportunity to see the ad. Review viewable impressions as a separate measure. Google Ad Manager’s overview of Active View summarizes the IAB display criterion as at least 50% of an ad’s pixels visible for one continuous second. For ads larger than 242,000 pixels, the threshold is at least 30% of pixels visible for one continuous second. These are viewability criteria, not promises that a person noticed, understood, or acted on the creative.
When reviewing campaign reports, compare served and viewable impressions and investigate placements where a large gap appears. Consider the placement and screen context: an ad positioned outside the visible browser area may be served without becoming viewable. Viewability is one diagnostic measure, not a substitute for whatever campaign outcome the advertiser is trying to evaluate. The sources cited here establish no general click-through, conversion, or campaign-performance rate, so the practices in this guide cannot be used to promise a particular result.
Handle common production problems
| Symptom | Likely issue | What to check |
|---|---|---|
| Creative is rejected by a publisher | The submitted asset or behavior does not meet that placement’s current requirements. | Recheck its accepted formats, dimensions or aspect ratios, file-size limits, animation rules, and submission notes. Do not substitute another publisher’s specifications. |
| Text or a disclosure is hard to read in the placement | The message was reviewed at a different size or presentation than the one where it runs. | Review the actual responsive states, simplify the hierarchy, and keep necessary qualification close to the relevant claim. |
| Banner appears slowly | Assets or code may be adding work before the creative can render. | Review the packaged HTML5 assets and remove unnecessary work before first display. Test the complete package through the intended ad-operations workflow. |
| Animation is rejected or behaves unexpectedly | The placement may restrict animation or impose its own duration or loop rules. | Check the destination publisher’s current rules. Apple News, for example, specifies no more than three GIF loops and 15 seconds total; that does not establish requirements for other placements. |
| Served impressions are higher than viewable impressions | Some delivered ads may not have met the viewability criterion. | Review viewable-impression reporting and investigate the placement and screen context, including whether the ad is often outside the visible browser area. |
| A visual screenshot does not match a live campaign | A page capture is only a view of that page at a particular capture context, not proof of live ad delivery. | Verify serving and acceptance using the publisher’s preview, ad-operations, and campaign-reporting processes. |
Use a pre-launch checklist
- Have you checked the current IAB portfolio and the destination publisher’s exact placement requirements?
- Does the creative fit the specified aspect ratio or size range without losing its message?
- Are the offer, call to action, and any necessary qualifications legible and understandable together?
- Is the asset package as lean as practical, and has the complete HTML5 creative been tested with the planned ad-operations workflow?
- Does the experience respect the reader’s content task, control, and choice?
- Will campaign reporting distinguish served impressions from viewable impressions?
Frequently Asked Questions
Does passing a publisher’s creative check guarantee that a banner will be accepted everywhere?
No. Acceptance requirements belong to the specific publisher and placement. Recheck them whenever the destination changes.
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Is a page screenshot enough to verify that a live ad campaign is working?
No. A screenshot records a visual state; use the publisher’s preview and ad-operations workflow to verify creative acceptance and campaign reporting to assess delivery.
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