Choosing banner dimensions is a media-planning decision as much as a design decision. The shape of a placement affects how much information can be shown, where the message can appear, and how the creative must be arranged. A familiar size is useful only when the publisher or platform accepts it and the composition remains legible in context.
Treat an ad-size list as a reference, not a ranking of guaranteed winners. This guide explains how to build a format plan around actual inventory, how to recompose rather than stretch a master design, and how to check the finished files. It also distinguishes fixed dimensions from flexible layouts, which is important when a team casually uses “standard banner” to describe several different production requirements.
Start with the placement, not the artboard
Ask where the campaign is expected to run. A desktop editorial rail, an in-content rectangle, and a small mobile slot have different spatial constraints. Get the accepted dimensions, supported formats, file limits, and delivery instructions from the actual buying destination. Keep that information with the brief rather than relying on a remembered specification from another campaign.
Build a placement matrix with one row per intended environment. Include the publisher or platform, the device context, the requested canvas, the destination URL, and the person responsible for approval. Mark unconfirmed inventory as unconfirmed. This prevents a production team from treating a speculative format as a booked placement.
The creative plan should follow this matrix. Producing a large library can be worthwhile, but only when the additional formats serve a specific distribution need. A smaller verified set is easier to approve, inspect, and maintain than a folder full of unused variations.
Know what fixed and flexible actually mean
A fixed-size ad is designed for a stated width and height, such as 300 × 250 pixels. A flexible ad can scale within an allowed range while retaining its defined relationship between width and height. The IAB Tech Lab New Ad Portfolio guidance describes an aspect-ratio-based approach to flexible sizing.
That distinction does not mean every existing placement has become flexible, or that every fixed canvas is obsolete in every buying environment. It means you need to identify the actual specification being requested. A fixed creative, a responsive container, and an asset-based ad assembled by a platform are related ideas, not interchangeable deliverables.
Ask the recipient a concrete question: do they want finished files in named pixel dimensions, a responsive HTML creative, or separate image and text assets? Answering that question early prevents an otherwise polished design from arriving in the wrong format.
Use rectangles to organize a compact story
The 300 × 250 medium rectangle and 336 × 280 large rectangle share a similar visual proportion. They offer room for a headline, a recognizable product or illustration, and a clear next step. That room is not an invitation to include every feature in the product brief.
Try sketching three blocks before designing details: recognition, promise, and action. Recognition is the brand or product cue. The promise explains the useful idea. The action tells a visitor where the click will lead. The order can change, but the three blocks should not compete at equal visual weight.
When translating between these rectangle sizes, inspect line breaks and safe margins rather than assuming the larger version can simply be reduced. Small type that looked comfortable on the larger artboard may become difficult to read in the smaller export. Review both at their actual display dimensions.
Let wide units stay genuinely simple
A 728 × 90 leaderboard has a very different reading pattern from a rectangle. It rewards short messages and a deliberate relationship between left and right. A logo, one idea, and an action can be enough. Trying to preserve a rectangle’s full copy usually creates tiny type or a crowded button.
A 970 × 250 billboard gives a wider composition more vertical room. Consider a strong product detail, an editorial-style headline, or a clear split between the promise and supporting imagery. Keep the action visible without forcing the viewer to decode several unrelated panels.
For both shapes, test the creative inside a page mockup with surrounding navigation and content. An ad that looks commanding on an empty slide may disappear among competing horizontal elements. Your goal is a readable hierarchy, not the maximum amount of material that fits inside the border.
Treat tall formats as a sequence, not a brochure
The 160 × 600 wide skyscraper is narrow enough to make long words awkward. Start with short lines and a limited number of visual elements. Check that the logo remains recognizable and that required qualifications do not become a dense block at the bottom.
The 300 × 600 half-page unit offers a broader vertical canvas. One useful approach is a top-to-bottom sequence: identify the problem, show the relevant product or offer, and finish with the next step. This is a suggested composition, not a rule that every campaign must follow.
Do not depend on the audience inspecting every inch of the unit. A visitor may encounter only part of the placement while scrolling. Keep the brand and main promise understandable without requiring the whole page to be studied. Use the available height to create rhythm rather than to reproduce a full sales page.
Rebuild the message for mobile
The 320 × 50, 300 × 50, and 320 × 100 formats are compact canvases. Start by deciding which parts of the larger message are essential. A short promise and clear brand cue may be more useful than a miniature image, two lines of explanation, and a cramped action label.
The taller mobile banner gives you more vertical space, but it still needs a mobile-first composition. Check that the words can be understood without zooming. Remove decorative details that become visual noise at the intended size. Compare variants on a real phone rather than judging them only in a desktop editor.
Also inspect the destination. A mobile creative that points to a difficult page creates an avoidable break in the journey. Our mobile banner guide pairs the canvas decision with readability, proportion, and post-click checks.
Separate dimensions from delivery requirements
Keep a production matrix
Width and height tell you the shape of the creative. They do not tell you the permitted file type, total bytes, animation behavior, click handling, or asset-hosting rules. Keep those requirements in separate columns of the production matrix. This makes differences between a static export and a packaged HTML creative visible.
Use the specification checklist before delivery. Confirm whether the destination distinguishes an initial load from additional assets, whether animation must stop, and whether a static fallback is needed. Check the exported file itself rather than a design-tool estimate. Compression and packaging can change what is actually delivered.
Name files so that another person can identify the campaign, size, creative concept, language, and version without opening each one. For example, a consistent internal naming scheme is more valuable than a sequence of files called “final,” “final-new,” and “approved-final-two.”
Choose coverage you can maintain
A useful format set balances opportunity with maintenance. Every extra size creates another place where an old price, broken destination, outdated condition, or superseded logo can survive. Assign one owner to the asset register and retire versions deliberately when an offer changes.
Review performance by meaningful placement and outcome, not by shape alone. A rectangle and a leaderboard can appear in different contexts, reach different audiences, and receive different budgets. Those differences make a simple size ranking difficult to interpret. Use the findings to refine the placement plan, then design a cleaner comparison when necessary.
The practical order is straightforward: confirm inventory, identify the deliverable, compose for the canvas, inspect the export, and keep the versions organized. The right dimensions get your message into the intended space. Clear creative and a coherent destination determine whether that space is being used well.
