1. Preview an ad tag by uploading the tag's HTML (script)
2. Get a live preview
3. View the landing page screenshot, URL, and query parameters
4. View network timelines, load times, file sizes, and more to ensure ads are compliant
5. Share with clients and get feedback

An HTML ad tag is a snippet of HTML markup that will load an ad in a web browser. The HTML often includes JavaScript, and it tells the browser how, where and when to load the ad.

Here's an example of an HTML ad tag from Google Campaign Manager 360. You can also test HTML5 ads and VAST video tags using our other tools:

When a user goes to a site, the user's browser sends info to the ad server. This info typically contains info on the user visiting the site and the ad's placement info. Then the ad server sends the ad tag to a third-party data provider so that it has the correct targeting info. It may also pass the tag to a number of other third parties for things like brand safety or geo-targeting.Then, the ad server sends the tag back to the advertisers and loads the ad in the user's browser which returns the ad tag with a creative URL that is likely hosted somewhere else as well.

Ad specifications are a set of metrics and rules to guide the design, production, and serving of ad creatives.
The Interactive Advertising Bureau (IAB) publishes ad creative guidelines that you can easily adopt or use as a starting point for defining your own ad specifications.

Once you have an ad tag specification in place, you can develop ad quality assurance (ad QA) checklists to ensure your ads always meet the spec.

The Network timeline allows you to see and analyze the network requests that make up each individual page load within a single user's session. In our case we're giving you a network timeline of an ad load. You can use this view to investigate the causes of slow ads and identify performance bugs.When we talk about "requests" in the context of the network timeline, we mean the line-by-line calls for the files that build an ad or send information from the browser to another system. Any given ad in your visitor's session may make requests for:

• HTML (the document that frames out the structure and content of a web page)
• Fonts (typography and icon sets)
• CSS (styles)
• JavaScript (scripts that make the page interactive or send data to other systems)
• Media (images and videos)

To test CM360 ad tags effectively:

1. Copy the full ad tag: Include the complete <ins> and <script> elements from CM360
2. Test in our validator: Paste the tag and generate a preview to see how it renders
3. Check performance: Review load times, file sizes, and network requests
4. Verify tracking: Ensure impression and click tracking pixels fire correctly
5. Test responsiveness: Check how the ad displays on different screen sizes

Our tool specifically supports CM360's dcmads.js library and will show you exactly how your ads perform in real browser environments.

First-party ad tags:

• Served directly from the publisher's domain
• Faster loading due to same-origin requests
• Better privacy compliance (no cross-domain tracking)
• Limited targeting and measurement capabilities

Third-party ad tags:

• Served from advertiser's or ad network's domain
• More complex targeting and tracking capabilities
• Cross-domain requests may be slower
• Better campaign measurement and attribution

Most programmatic advertising uses third-party tags for advanced targeting. Our tester works with both types and shows the network implications of each approach.

Common issues and solutions for non-loading ad tags:

Script blocked by ad blockers

Test in incognito mode or with ad blockers disabled

HTTPS/HTTP mixed content errors

Ensure all resources use HTTPS on secure pages

JavaScript errors

Check browser console for error messages and fix syntax issues

Cross-origin restrictions (CORS)

Verify that ad server allows cross-domain requests

Timeout issues

Optimize ad creative file sizes and server response times

Invalid HTML syntax

Validate HTML structure and fix malformed tags

Our network timeline analysis helps identify exactly where ad loading fails, making troubleshooting much easier.

We support all major ad tag formats including:

• Google Campaign Manager 360: DCM ads with dcmads.js library
• Google Display & Video 360: DV360 tags with advanced targeting
• Amazon DSP: Amazon advertising platform tags
• Facebook/Meta: Social media advertising tags
• Generic JavaScript: Custom ad server implementations
• iFrame tags: Sandboxed ad content delivery
• Image tags: Simple banner ad implementations

Simply paste your ad tag HTML and our validator will automatically detect the format and apply appropriate testing criteria.

To minimize ad impact on page loading performance:

1. Use async loading: Load ad scripts asynchronously to avoid blocking page render
2. Implement lazy loading: Only load ads when they're about to become visible
3. Optimize creative sizes: Compress images and minimize file sizes
4. Reduce redirects: Minimize ad server redirect chains
5. Cache static assets: Use CDNs and proper cache headers for ad resources
6. Monitor performance: Regularly test ad loading times and optimize

Our performance analysis shows exactly how your ads affect page loading and identifies specific optimization opportunities.