What are Display Banner Ads?

A 2025 guide for marketers, founders, and media buyers

Display banner ads are the rectangular (and sometimes skyscraper-tall or billboard-wide) visuals you see across websites and apps. They’re the workhorses of digital advertising: quick to launch, easy to test, broadly targetable, and measurable end-to-end. This guide breaks down how they work today — formats, specs, targeting, measurement, creative best practices, and how to get the most from your spend.

What exactly is a display banner ad?

At its core, a display banner ad is a visual placement—image, lightweight animation, or HTML5 creative — served into a publisher’s ad slot through an ad network or programmatic exchange. Unlike text-only search ads, banners are visual and appear across the open web and in mobile apps. They can be bought directly from publishers, via networks such as the Google Display Network, or through demand-side platforms (DSPs) that bid in real time. Google also offers responsive display ads that assemble your uploaded assets (images, headlines, descriptions, logos) into many size variations and auto-optimize for performance. (Google Help)

Why banner ads still matter

Despite periodic predictions of their demise, banners remain one of the most flexible, scalable ways to generate awareness, retarget high-intent visitors, support product launches, and feed the top and middle of your funnel. They’re comparatively fast to produce, can be localized and versioned at scale, and offer mature controls for brand safety, frequency, and measurement that performance teams expect.

The ecosystem in a nutshell

Publishers: The sites and apps with ad inventory.
Ad servers & exchanges: The pipes that deliver and auction impressions.
DSPs: Tools advertisers use to target, bid, cap frequency, and measure.
Networks: Bundles of inventory with pre-set targeting (e.g., interest, topic).
Verification vendors: Viewability, brand safety, and fraud protection.
Attribution & analytics: From platform pixels to MMM.

On Google’s side, you’ll encounter Display campaigns (including asset-based responsive ads) and options like audience and contextual targeting modes, each configurable under “Targeting” or “Observation” in campaign settings. (Google Help)

Common banner formats (and when to use each)

Static image banners

Raster images (PNG/JPG/WebP). Fastest to make, universally accepted, and ideal for awareness, always-on presence, or retargeting where message clarity beats motion.

Animated GIF banners

Looping frames in a single file. Great for a little movement without the production overhead of video. Keep motion purposeful and legible at small sizes. (Always check each platform’s latest policies on animation duration and weight.)

HTML5 (rich media) banners

Interactive, CSS/JS-powered animations packaged in a ZIP. They deliver smooth motion at small file sizes and allow more advanced effects, polite loading, and dynamic features. Often the preferred choice for performance-oriented campaigns and programmatic buys. (Exact ZIP size and asset limits vary by platform; consult the current spec of your ad server or network.) (Integral Ad Science)

Responsive display ads (Google)

You upload building blocks (images, headlines, descriptions, logos); the system assembles and serves optimal combinations across placements. This maximizes reach and reduces manual resizing while Google’s machine learning optimizes delivery. (Google Help)

Standard sizes you’ll see everywhere

While the web supports many dimensions, a small set covers the majority of available inventory. The 300×250 (Medium Rectangle), 728×90 (Leaderboard), 300×600 (Half Page), 160×600 (Wide Skyscraper), 320×50 (Mobile Leaderboard), and 970×250 (Billboard) are among the most common across ad managers and exchanges. Google Ad Manager’s reference lists these and other popular display sizes you’ll encounter when trafficking campaigns. (IAB Tech Lab)

Tip: Build a “core set” to cover reach (e.g., 300×250, 728×90, 300×600, 320×50) and then add 970×250 or 336×280 where publisher mixes justify it.

File weights, specs, and QA

Every network enforces limits on file size, dimensions, animation behavior, click-through handling, and more. For example, Google outlines creative specs and best practices for its display formats (including its asset-based responsive display ads), and you should always reference the current spec before exporting. Build a QA checklist: verify dimensions, final weight, clickTags (for HTML5), landing URL, animation smoothing, and device rendering. (Google Help)

Targeting: who sees your banners (and why)

Modern display buys blend audience and contextual signals:

Contextual: Match pages by topic/keywords (privacy-friendly, resilient).
Audience: Use in-market, affinity, first-party lists, and remarketing.
Placement: Hand-pick sites, apps, or specific sections.
Automated: Let algorithms expand reach to similar inventory.

On Google, you can set segments to Targeting (restrict delivery) or Observation (gather insights without narrowing reach), then optimize based on performance. (Google Help)

Life after third-party cookies

Chrome’s Privacy Sandbox introduces APIs such as Topics for interest-based advertising without cross-site tracking. If you’re planning long-term display strategy, expect more contextual and first-party approaches, augmented by these privacy-preserving signals. (Google Help)

Viewability and attention: what counts as “seen”?

The long-standing industry benchmark (used by platforms and verification vendors) is the MRC viewable impression: at least 50% of pixels in view for 1 continuous second for display (and 2 seconds for video). Buy, optimize, and report with this in mind; many advertisers prefer viewable CPM buying to avoid paying for unseen impressions. (Google Business)

Creative that works: the anatomy of an effective banner

1) One message, one action

Banners are tiny. Pick a single value prop and a clear CTA (“Shop now,” “Get pricing,” “Start trial”). Responsive display ads may swap copy combos, but each creative instance should still read as one message. (Google Help)

2) Visual hierarchy

Lead with brand or product, then the benefit, then the action. Use contrast for legibility at small sizes (especially 300×250 and 320×50).

3) Motion with a job

For GIF/HTML5, animate what matters: benefit, differentiator, or offer. Avoid jittery loops. Ensure frames resolve to a CTA or lockup.

4) Keep it light

Respect platform weight limits and avoid heavy assets. For HTML5, lean on vector shapes, sprite sheets, compressed images, and polite loading.

5) Design for the container

Remember surrounding content. Simple backgrounds and bold type survive busy publisher pages.

6) Test like a scientist

Iterate headlines, CTAs, product crops, and colorways. Use Observation settings or experiments to learn without disrupting delivery. (Google Help)

User experience and standards you shouldn’t ignore

Intrusive formats (e.g., auto-play with sound, pop-ups that block content) contribute to ad fatigue and blocking. The Coalition for Better Ads documents experiences people find most annoying; designing within these guardrails improves user trust and reduces the risk of enforcement by browsers and platforms. Google’s guidance aligns with these standards to help publishers and advertisers maintain a good ad experience. (Assemble Studio, CyberOptik)

Measurement: beyond CTR

Click-through rate is directional, not destiny. Build a scorecard:

Reach & frequency: Are we hitting enough unique users, with controlled exposure?
Viewability: Optimize for placements above the fold and sticky units. (Google Business)
On-site behavior: Post-click engagement (bounce, pages/session, time to value).
Conversion & assisted lift: Track last-click and view-through where policy allows.
Cost efficiency: CPMs for awareness, CPC/CPA for lower-funnel experiments.
Incrementality: Geo or audience splits, MMM, or platform experiments to prove lift.

Production workflow (what good teams do)

Brief: Audience, goal, offer, brand assets, mandatory copy, landing URL, sizes, and platform mix.
Concept: Thumbnail variations of layout and hierarchy; decide what animation (if any) has a job to do.
Build: Static (PNG/JPG/WebP), GIF (compact loop), or HTML5 (ZIP with HTML/CSS/JS assets) — or upload assets for responsive display ads to assemble permutations. (Google Help)
QA: Dimensions, weight, click handling, anti-aliasing on type, animation smoothness, hover states (for HTML5), and device rendering.
Traffic: Map sizes to placements; set frequency caps; choose targeting vs. observation. (Google Help)
Optimize: Swap lowest-performing variants, expand winners to more sizes, iterate weekly.

Common mistakes (and how to avoid them)

Too much text: If it reads like a brochure, it won’t get read.
No CTA: Even awareness creatives should steer the next step.
Illegible at small sizes: Tiny copy and low contrast vanish on mobile.
Heavy files: Bloated GIFs and uncompressed images tank delivery.
Mismatched landing pages: Visual or message disconnects hurt conversion.
Ignoring responsive ads: Asset-based formats can unlock reach with minimal effort. (Google Help)

How to choose the right format for your goal

Need speed and scale? Use responsive display ads to cover many sizes without hand-building every variant. (Google Help)
Budget-friendly awareness or retargeting? Static banners are cost-effective and universally accepted.
A touch of motion, minimal complexity? Animated GIFs introduce movement without going full video.
Performance and polish? HTML5 delivers smooth animations, interactivity, and lean file sizes — well-suited for programmatic buys. (Integral Ad Science)

A quick checklist before you launch

You’ve built the core sizes your plan needs (e.g., 300×250, 728×90, 300×600, 320×50). (IAB Tech Lab)
Copy fits one message + one CTA.
Assets meet current platform specs (weight, dimensions, behavior). (Google Help)
Frequency cap set, viewability monitored, placements brand-safe. (Google Business, Assemble Studio)
You’ve prepared two or three simple variants to test in week one.

The bottom line

Display banner ads remain a foundational channel: affordable, adaptable, and measurable. Pair tight creative (clear message, strong CTA, right motion), coverage of common sizes, privacy-aware targeting, and disciplined testing. Whether you hand-craft static/HTML5 units or feed assets into responsive display, the ingredients for performance haven’t changed — clarity, relevance, and relentless iteration. (Google Help, Google Business)