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Everything You Need to Know about Banner File Sizes in Display Advertising

8 minutes read

File size is usually not the first property that comes to mind when creating banners for a display ad campaign.

That is until you reach the publishing point.

All ad networks have limitations in place or at least file size recommendations that you must follow to upload your assets successfully.

But there’s more to file sizes than an imaginary kilobytes line that you must not cross.

They can actually help you harvest more impressions and increase your campaign’s overall performance.

Stick with me as I walk you through how display ad file sizes are measured, why they matter, and which are the recommended file sizes for the most popular ad networks.

How Is Display Ad File Size Measured?

Let’s start with the basics. 

If you’re familiar with the file size units of measurement, feel free to jump straight to the part about why display ad size matters or check the standard display ad banner sizes.

File size, also known as file weight, represents the amount of space a file takes up on a storage medium like a computer hard drive or a server.

It is measured in bytes and larger units that we get by adding metric prefixes like “kilo-”, “mega-”, “giga-”, and so on.

The most common units of measurement are:

  • 1 B (byte) = 1 byte
  • 1 kB (kilobyte) = 1.000 bytes
  • 1 MB (megabyte) = 1.000 kB or 1.000.000 bytes
  • 1 GB (gigabyte) = 1.000 MB, 1.000.000 kB, or bytes
  • 1 TB (terabyte) = 1.000 GB, 1.000.000 MB, kB, or bytes

You’ll mostly be seeing the first four units of measurements when dealing with display ads file sizes, as they are usually not large enough to be measured in GB or TB.

Make sure you don’t confuse display ad file size with pixel size (commonly known simply as size), as the latter refers to the width and height of our display ad visuals expressed in pixels.

Let’s take the display banner below as an example. Its size is 300 x 250 pixels while its file size is 49 kB.

If you want to check for yourself, save the file onto your computer and do the following depending on your operating system:

  • Windows: Right click on the file -> go to Properties -> Details tab -> See image dimensions for pixel size and file size.
  • macOS: Select the file -> ctrl + click -> Get Info -> Look for size under General and dimensions under more info.

Now that we’ve established they are not one and the same, let’s talk a bit about the relationship between the two. 

A decrease in pixel size causes a drop in file size. Let’s take a 970 x 250 pixels display ad of 109 kB.

Now let’s resize it to, let’s say, 530 x 137 pixels, maintaining the same ratio.

Our resized image has a file size of only 38.4 kB.

However, this is a guaranteed result only in the case of a resize.

If you have two different display ads and one of them happens to be smaller in pixel size than the other, it does not mean it automatically has a smaller file size too.

Other factors at play could influence the outcome, like the type of digital assets you use to create the banner.

Check out these two JPG display ads. We have a 120 x 240 vertical banner of 32.5 kB on the left, and on the right, a 300 x 250 medium rectangle of 27.9 kB.

Although smaller in pixel size, the vertical banner has a larger file size than the medium rectangle due to more creative assets being used for its creation.

The type of display ad file format also affects the amount of storage space it uses, hence the file size.

I exported this banner made in Creatopy in two different file formats to see how this variable influences file size.

Even though the two banners are identical in pixel size and are made up of precisely the same digital assets, the PNG version on the left resulted in a 7.70 kB file size, and the JPG version on the right resulted in a 22.6 kB file size.

Why Display Ad File Size Matters

Display ad files are temporarily downloaded on the users’ computers when they open a web page, so the heavier the files, the longer it will take to load that web page.

For instance, if there are five large file size display ads on a web page, the loading time will grow significantly.

Users expect a website to load quickly, so some of them might not wait for the page to be displayed, and you’ll lose impressions.

To ensure your ads render before the scroll and users get to the point of clicking, you must keep your ads’ file sizes on the smaller side to reduce the loading time.

Moreover, Google favors websites with faster loading times in search results rankings, which further increases the chance of your display ads being seen by more people.

But how big is too big?

This question puzzled advertisers and prompted ad publishers to set some restrictions regarding the standard file size of the display ads they accept. 

Besides, a set of universally accepted standards for display ad file sizes was created by the Interactive Advertising Bureau (IAB).

IAB Standard Banner Sizes

The IAB is an organization that supports online advertising by developing technical standards and best practices for the industry.

Their New Ad Portfolio comprises official guidelines for display advertising meant to improve the advertising experience across multiple platforms.

Note that the initial load refers to the total of files the browser requires for the initial ad display.

Subload, also known as host-initiated subload, is the additional file size the browser loads in the background. 

For example, if the maximum file size for the initial load is 50 kB, anything between 50 kB and the max for subload is downloaded in the background. At the same time, the ad is already being displayed.

Fixed Size Ad Specifications

Ad unit Name Fixed Size (px) Max. K-Weight (kB)
Initial Load Subload
Billboard 970×250 250 500
Smartphone Banner 300×50 or 320×50 50 100
Leaderboard 728×90 150 300
Super Leaderboard/Pushdown 970×90 200 400
Portrait 300×1050 250 500
Skyscraper 160×600 150 300
Medium Rectangle 300×250 150 300
Button 120×60 50 100
Mobile Phone Interstitial 640×1136 or 750×1334 or 1080×1920 300 600
Feature Phone Small Banner 120×20 5 N/A
Feature Phone Medium Banner 168×28 5 N/A
Feature Phone Large Banner 216×36 5 N/A

Flexible Size Ad Specifications

Ad Unit Name Ad Size Size Range Max. K-Weight (kB)
Min. Size Max. Size Initial Load Subload
Half Page 900×450  1800×900 250 500
Billboard 970×250 900×225 1800×450 250 500
Smartphone Banner 300×50, 320×50 300×50 450×75 50 100
Leaderboard 728×90 600×75 1200×150 150 300
Super Leaderboard/Pushdown 970×90 900×90 1800×180 200 400
Portrait 300×1050 300×900 450×1350 250 500
Skyscraper 160×600 160×640 240×960 150 300
Medium Rectangle 300×250 300×300 450×450 150 300
Small Banner N/A N/A 120×20 5 N/A
Medium Banner N/A N/A 168×28 5 N/A
Large Banner N/A N/A 216×36 5 N/A

Google Ads Recommended Display Ad File Size

Being the most popular ad network on the market, Google Ads has its own specs for display ads.

Ad type Ad size (px) Max. file size (kB)
Static ads Animated ads*
Small square 200×200 150 150
Vertical rectangle 240×400 150 150
Square 250×250 150 150
Triple widescreen 250×360 150 150
Inline rectangle 300×250 150 150
Large rectangle 336×280 150 150
Netboard 580×400 150 150
Skyscraper 120×600 150 150
Wide skyscraper 160×600 150 150
Half-page ad 300×600 150 150
Portrait 300×1050 150 150
Banner 468×60 150 150
Leaderboard 728×90 150 150
Top banner 930×180 150 150
Large leaderboard 970×90 150 150
Billboard 970×250 150 150
Panorama 980×120 150 150
Mobile banner 300×50 150 150
Mobile banner 320×50 150 150
Large mobile banner 320×100 150 150

*The recommended file size for HTML5 display ads is 150 KB or smaller.

If you’re interested in finding more about standard display ad sizes, you can read this article on the top performing banner ad sizes for Google ads.

File Size Requirements for Different Ad Networks

Amazon Ads 

Ad type Ad size (px) Max. file size (kB)
Static ads HTML ads
Medium Rectangle 300×250 40 200
Leaderboard 728×90 40 200
Wide Skyscraper 160×600 40 200
Large Rectangle 300×600 50 200
Billboard 970×250, 800×250 (Germany only) 200
Mobile Leaderboard 320×50 50
Mobile Detail and Search Results page 414×125 100
Mobile Medium Rectangle 300×250 40
Mobile Leaderboard (Tablet) 728×90 200

See Amazon’s desktop ad specifications and mobile ad specifications for more details.

Yahoo Ads

Ad type Ad size (px) Max. file size (kB)
Initial Load Subload
Aol Mail Send Confirm 1200×800 200
Button 120×60  80 80
Skyscraper 160×600 150 300
Medium Rectangle 300×250 150 300
Mobile Banner 300×50 50 100
Half Page 300×600 200 400
Mobile Interscroller 320×480 300 600
Mobile Interstitial 640 x 960 300 600
Mobile Banner 320×50 50 100
Leaderboard 728×90 150 300
Tablet Interstitial 768×1024 300 600
Billboard 970×250 250 500

For detailed recommendations go to Yahoo Ad’s specifications page.

How to Reduce the File Size of Your HTML5 Display Ads

Some HTML5 ads may need larger file sizes to be displayed properly. While optimizing image display ads is simply a matter of compressing the files, HTML5 ads are a different story.

Let me share some tricks you can apply to get your HTML5 banner file size to where you want it.

  • Replace PNG or JPG files with SVG ones because they have smaller file sizes and render faster;
  • If you stick with JPG or PNG images, compress them using a tool like Tinypng, which preserved image quality;
  • Lower the size of your HTML, CSS, and JavaScript files with an online tool like JScompress or HTMLcompressor. You don’t need to worry about this when using Creatopy because all code files are optimized for advertising platforms;
  • Remove unnecessary assets like images, shapes, or text, if need be, because every element you use for your banner adds to the file weight. 
  • Go for a simpler animation that uses simple movements and fewer transitions.

That being said, there’s a much easier way to ensure your display ad file size is the right one, regardless of file format.

Creatopy’s Ad Serving feature allows you to publish ads of any file size and format on 24 ad platforms, including Google Ads, Adform, Epom, Roku,, and Xandr.

Curious how it helps you bypass file size limitations? It’s simple. The designs you make in Creatopy are hosted on our servers, and you are given ad tags for quick ad delivery to the platforms of your choice.

Ad serving is part of Creatopy’s Optimize plan, meaning that if you are currently using the Create or Automate plans, you’ll need to upgrade to access it.

Final Thoughts

Ad networks’ recommended display ad file sizes aren’t there to limit you but to ensure you achieve the optimal weight for quick ad rendering, helping you reach a wider audience in the process.

There are simple ways to reduce your ads’ file size before upload, or you can eliminate the cap by using tools such as Creatopy’s ad serving. 

Either way, whether you think they are helpful or could do without them, file size restrictions are a given that all display advertisers must be mindful of.

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