Meta Ad Specs: What Gets Your Creative Rejected and Why

Meta ad specs define the technical requirements your creative must meet before it runs across Facebook, Instagram, Messenger, and the Audience Network. Get them wrong and your ad either gets rejected outright or runs in a degraded format that quietly kills performance before you ever see a result worth analysing.

This is not a glamorous topic. But after years of managing hundreds of millions in ad spend across 30 industries, I can tell you that more campaigns underperform because of avoidable technical failures than because of bad strategy. Spec errors are the silent tax on creative investment, and most teams pay it without realising.

Why Ad Specs Are a Strategic Issue, Not Just a Technical One

I have sat in enough creative reviews to know how this usually goes. The brief goes out, the creative team builds something genuinely good, and then someone in production realises the video is the wrong aspect ratio or the image is 200KB over the file size limit. The fix is rushed, quality drops, and the campaign goes live in a compromised state. Nobody talks about it. The results come back soft and the conversation turns to targeting or bidding, when the real problem was upstream.

Ad specs are a strategic issue because they shape what your creative can actually do in the wild. A video built at 16:9 for desktop consumption will be pillar-boxed on mobile Stories, shrinking your visual to a fraction of the screen and handing the rest to black bars. That is not a minor inconvenience. On a platform where the thumb moves in under two seconds, losing screen real estate is losing attention, and losing attention is losing money.

If you are thinking about how paid social fits into a broader go-to-market approach, the Go-To-Market and Growth Strategy hub covers the planning frameworks that sit above channel execution, including how to sequence paid activity against business objectives rather than just optimising in isolation.

Meta Ad Specs by Placement: The Numbers That Matter

Meta runs ads across a range of placements, and each one has its own technical requirements. The table below covers the placements that account for the vast majority of spend and where spec errors do the most damage.

Facebook and Instagram Feed

Feed placements remain the workhorse of most Meta campaigns. The format is forgiving by Meta’s standards, but that forgiveness disappears the moment you push outside the boundaries.

For image ads in Feed, the recommended aspect ratio is 1:1 for square or 1.91:1 for landscape. Portrait at 4:5 also works well and tends to take up more vertical screen space on mobile, which matters. The minimum image resolution is 1080 x 1080 pixels for square. File size must stay under 30MB, and the accepted formats are JPG and PNG. Avoid GIFs in Feed image placements as they are not natively supported and will be treated as static images.

For video ads in Feed, the recommended aspect ratio is again 4:5 for mobile-first delivery, though 1:1 is a safe fallback. The minimum resolution is 1080 x 1080 pixels. Video length can run up to 241 minutes technically, but in practice anything beyond 15 seconds for a cold audience is working against you. File size limit is 4GB. Accepted formats include MP4, MOV, and GIF. Frame rate should be at minimum 30fps, and H.264 compression is the standard. Audio is recommended at stereo and 128kbps minimum.

One thing I have seen trip up even experienced teams: Meta’s primary text field in Feed has a 125 character recommended limit before it gets truncated with a “see more” prompt. You can write more, but if your key message sits beyond that threshold, most users will never read it.

Stories and Reels

Stories and Reels are where the spec gap between what teams produce and what the platform needs is widest. These placements are built for 9:16 vertical video, full stop. If you are not shooting or editing in 9:16, you are already behind.

For Stories image ads, the required aspect ratio is 9:16 with a minimum resolution of 1080 x 1920 pixels. File size must be under 30MB. The safe zone matters here: Meta crops the top and bottom of Stories images to accommodate the UI, so keep all critical visual elements and text within the central 1080 x 1420 pixel zone. Anything outside that zone risks being obscured by the profile icon, call-to-action button, or swipe-up prompt.

For Stories video ads, the same 9:16 ratio applies with a minimum resolution of 1080 x 1920 pixels. Maximum video length for Stories is 60 seconds, though Meta recommends 15 seconds or under for performance. File size limit is 4GB. The same safe zone rules apply as for image ads.

Reels ads follow similar vertical specs: 9:16 ratio, 1080 x 1920 pixel minimum resolution, and a video length of 15 to 60 seconds. Reels is increasingly where Meta is pushing organic reach, which means ad placements in Reels are appearing alongside content that is natively vertical, natively fast, and natively produced for the format. A horizontally shot ad dropped into Reels does not just look out of place technically. It signals to the viewer immediately that what they are watching is an ad, which is the fastest way to lose them.

Messenger and Audience Network

Messenger inbox ads appear between conversations and follow similar specs to Facebook Feed: 1:1 or 1.91:1 aspect ratio, minimum 1080 x 1080 pixels, under 30MB for images. Messenger Stories follow the same 9:16 requirements as Facebook and Instagram Stories.

The Audience Network is where things get complicated. This is Meta’s extended placement network running across third-party apps and websites, and it supports a wider range of ad formats including native, banner, and interstitial. The spec requirements vary by format within the Audience Network, and the honest advice is to treat it as a separate placement decision rather than a default extension of your Feed campaigns. The inventory quality and context vary significantly, and creative built for Feed rarely translates cleanly to Audience Network formats.

Carousel and Collection Formats

Carousel ads allow between 2 and 10 cards, each with its own image or video. Each card image should be 1080 x 1080 pixels at a 1:1 ratio. Each card video follows the same resolution requirement with a maximum length of 240 minutes per card, though in practice carousel videos should be short, 10 to 15 seconds per card at most. File size limits are 30MB per image card and 4GB per video card. Headline text per card is recommended at 32 characters or fewer before truncation.

Collection ads, which are mobile-only and pair a cover image or video with a product catalogue, require a 1:1 or 1.91:1 ratio for the cover asset. The cover image should be at least 1080 x 1080 pixels. Collection ads open into an Instant Experience when tapped, which has its own set of asset requirements depending on how the template is configured.

The Text-on-Image Problem That Never Fully Goes Away

Meta officially retired the strict 20% text rule a few years ago. Before that, any image ad where text covered more than 20% of the image area would either be rejected or have its reach significantly restricted. The hard cap is gone, but the underlying principle is not.

Meta’s delivery system still penalises image ads with heavy text coverage by reducing their reach and increasing their effective cost. The algorithm interprets heavy text on images as lower quality creative, and it prices that assessment into your delivery. So while you will not necessarily get a rejection notice, you will pay more to reach fewer people with a text-heavy image than you would with a clean visual.

The practical rule is still to keep text on images minimal. If you need to communicate a message in text, use the primary text, headline, and description fields in the ad unit itself. That is what they are for. Overlaying your headline onto the image as well is doubling up in a way that costs you delivery efficiency and often looks cluttered.

Early in my agency career I was much more focused on squeezing every message into every available pixel of an ad. It felt like thoroughness. What I learned over time, partly from watching campaigns across dozens of categories, is that the ads that perform consistently tend to have one clear visual idea and one clear message. Not because simplicity is a virtue in itself, but because the platform is competitive and attention is short. You do not win by saying more. You win by saying the right thing clearly.

Advantage+ Placements and What They Do to Your Creative

Meta’s Advantage+ placements (previously called automatic placements) distribute your ad across all eligible placements based on where Meta predicts you will get the best results for your objective. The appeal is efficiency. The risk is that Meta will crop and adapt your creative to fit placements it was not designed for, sometimes in ways that compromise the visual.

When you use Advantage+ placements, Meta will attempt to fit your creative into every placement it deems relevant. A 1:1 image built for Feed will be used in Stories, where it will be pillar-boxed. A 9:16 video built for Stories will be used in Feed, where it may be cropped to 4:5 or 1:1. Meta gives you the option to preview how your creative will appear across placements before you publish, and using that preview is not optional if you care about how your ads actually look.

The better approach, if budget allows, is to build placement-specific creative. That means a 9:16 version for Stories and Reels, a 1:1 or 4:5 version for Feed, and separate assets for any Messenger placements you are running intentionally. This costs more in production but removes the guesswork from how Meta will adapt your creative, and it gives you cleaner data on what is actually working at the placement level.

I spent a significant part of my time at iProspect working through exactly this kind of operational detail with clients who were scaling paid social. When we grew the team from around 20 people to close to 100, one of the things that changed was how seriously we took creative production as a performance lever. The accounts that produced placement-native creative consistently outperformed the accounts that relied on Meta to adapt a single asset. The gap was not marginal.

File Size, Format, and the Silent Failures

File size errors are the most frustrating category of spec failure because they often do not generate a clear error message. An image that is slightly over the 30MB limit may simply fail to upload without explanation. A video that exceeds 4GB may appear to upload and then fail at the processing stage. Teams spend time troubleshooting what looks like a platform bug when the actual issue is a file that is too large.

For images, JPG is almost always the right format choice. PNG is appropriate when you need transparency, but PNG files are typically larger than JPG at equivalent quality, which means you are more likely to hit the file size ceiling. Compress images before upload using a tool that preserves visual quality. Exporting directly from design software at maximum quality and uploading without compression is a common production mistake.

For video, MP4 with H.264 encoding is the standard. MOV files work but tend to be larger, which brings you closer to the 4GB ceiling. If you are working with high-resolution video, compress it to H.264 before upload rather than relying on Meta’s processing to do the work. The output quality from Meta’s compression is acceptable but not optimal, and you have more control over the result if you compress on your end first.

Audio in video ads is worth paying attention to. A significant proportion of Meta video ads are watched without sound, particularly in Feed where autoplay is silent by default. This does not mean audio does not matter. It means your video needs to work without it. Captions are not just an accessibility feature. They are a performance feature. Meta’s automatic captioning tool in Ads Manager is functional but imperfect, so review and edit captions before the ad goes live.

Character Limits and Copy That Gets Truncated

Meta’s ad copy fields have recommended character limits that differ from hard limits. Exceeding the recommended limit does not prevent the ad from running, but it does mean your copy gets cut off in the ad unit with a “see more” prompt. Whether users click that prompt depends on how engaging your opening copy is, and in most cases they do not.

The recommended limits by field are as follows. Primary text: 125 characters. Headline: 27 characters. Description: 27 characters. These are tight. They force clarity, which is not a bad thing. If you cannot communicate your core proposition in 125 characters of primary text, the problem is usually not the character limit.

The headline field is the one that causes the most frustration. 27 characters is roughly four to five words. That is not much room for nuance, but it is enough room for a clear, specific claim. “Free delivery over £50” fits. “Discover our range of premium handcrafted leather goods” does not, and trying to force it in just means the truncated version reads as incomplete.

One pattern I see repeatedly in campaign audits: teams write long, detailed primary text because they are used to writing for email or landing pages, and then they wonder why engagement is low. The ad unit is not the place for the full argument. It is the place for the hook that earns the click. The landing page is where you make the case.

How Spec Compliance Connects to Campaign Structure

Getting specs right is a prerequisite for running campaigns that can be properly evaluated. If your creative is technically compromised, you cannot draw reliable conclusions from performance data. You might attribute underperformance to the audience, the bid strategy, or the offer, when the actual problem is that your video was pillar-boxed in Stories and nobody watched past the first frame.

This connects to a broader point about how paid social fits into a go-to-market strategy. When I was judging at the Effie Awards, one thing that separated the campaigns that worked from the ones that did not was operational discipline. The winning work was not just strategically sound. It was executed cleanly. The creative was built for the platform. The targeting was coherent. The measurement was honest. None of that is possible if the foundation is technically compromised.

There is a tendency in marketing to treat technical compliance as a production detail that sits below the strategic conversation. That is a mistake. Specs are the contract between your creative intent and what the platform actually delivers to the audience. Breaking that contract, even accidentally, has real commercial consequences.

For context on how paid social fits within broader go-to-market thinking, including how to sequence channels and set objectives that connect to business outcomes rather than platform metrics, the Go-To-Market and Growth Strategy hub is worth working through before you get into the execution detail.

Understanding how platforms like Meta fit into a broader scaling approach is also something that BCG’s work on scaling agile organisations touches on indirectly. The principle that operational rigour enables strategic speed applies as much to marketing execution as it does to product development. Sloppy execution forces you to spend time troubleshooting rather than optimising.

On the measurement side, Vidyard’s analysis of why go-to-market feels harder makes the point that fragmented execution across channels is one of the primary reasons teams struggle to attribute results accurately. Spec compliance is one layer of that fragmentation problem. When creative is running in degraded formats across multiple placements, the performance data becomes difficult to interpret.

For teams thinking about how creator content fits into Meta campaigns, Later’s guidance on go-to-market with creators is useful context. Creator content often comes in formats that are natively vertical and natively short, which means it tends to be closer to spec compliance by default than agency-produced creative. That is not an argument for replacing one with the other. It is an argument for understanding what each format does well.

The commercial case for getting specs right is straightforward. Clean creative that meets platform requirements runs more efficiently, reaches more people for the same budget, and generates data you can actually use to make decisions. The alternative is paying a technical tax on every campaign you run, without ever seeing it itemised on an invoice.

A Quick Reference for the Specs That Matter Most

For teams that need a working reference rather than a full read, here is the condensed version of the specs that cause the most problems in practice.

Feed image ads: 1:1 or 4:5 aspect ratio, minimum 1080 x 1080px, JPG or PNG, under 30MB, primary text under 125 characters, headline under 27 characters.

Feed video ads: 4:5 or 1:1 aspect ratio, minimum 1080 x 1080px, MP4 or MOV with H.264 encoding, under 4GB, minimum 30fps, 15 seconds or under for cold audiences, captions recommended.

Stories and Reels image ads: 9:16 aspect ratio, minimum 1080 x 1920px, under 30MB, keep critical elements within the central safe zone of 1080 x 1420px.

Stories and Reels video ads: 9:16 aspect ratio, minimum 1080 x 1920px, MP4 or MOV, under 4GB, maximum 60 seconds for Stories and Reels, 15 seconds recommended, same safe zone rules apply.

Carousel ads: 2 to 10 cards, each card at 1:1 ratio, 1080 x 1080px minimum, under 30MB per image card, under 4GB per video card, headline per card under 32 characters.

These are the specs as of the time of writing. Meta updates its requirements periodically, and the Ads Manager creative tools will flag spec issues at the ad level before you publish. Use that preview. It is the fastest way to catch problems before they cost you.

For broader market context on how paid social fits into demand generation and market penetration strategies, Semrush’s overview of market penetration provides a useful framework for thinking about where Meta advertising sits in the growth mix. And for teams thinking about pipeline contribution from paid channels, Vidyard’s Future Revenue Report covers the gap between content investment and measurable pipeline outcomes in useful detail.

About the Author

Keith Lacy is a marketing strategist and former agency CEO with 20+ years of experience across agency leadership, performance marketing, and commercial strategy. He writes The Marketing Juice to cut through the noise and share what works.

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