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How Much Headline Copy Is Too Much?
May 5, 2022

Headlines are the first impression of most ads, but like a first date, how do you know if they are coming on too strong (or blending into the woodwork)? We analyzed data to observe how headline length and font size are related to CTR performance.

In this series, Engaging Creative, we’ll dig into questions we get from clients about key levers of creative effectiveness and apply analytics to test hypotheses about the drivers of performance. 

What makes a good headline?

There’s no shortage of industry best practices or creative recommendations on what constitutes a great headline. Make it provocative. Pose a question. Write like you talk. The list goes on. 

One of the most important, but often overlooked, criteria of a good headline is legibility. Make the type too small and viewers will have to grab their glasses to read your ad. If the type is too large, in the best case scenario, you cut down the amount of information you can convey. In the worst case, it can come across like your brand is yelling at the viewer. These challenges are especially pervasive in digital advertising where the real estate an ad takes up on a page is often low and the attention of the viewer can be elsewhere if advertising content isn’t compelling.

Headline legibility is critical to the success of  every impression of an advertisement…but by how much? And what does legible mean in an industry with so many creative possibilities?

But first, Facebook has opened a window on the matter.

In late 2020, Facebook quietly announced it would remove an approval algorithm baked into its platform that screened ads to ensure no more than 20% of visual space contained text. While this rule often caused creative approval headaches for marketers, it gave a benchmark for the ideal amount of text an ad should contain on the platform. With restrictions lightened on Facebook, brands now have more creative opportunities to explore with text on their ads on social media in addition to the opportunities granted by channels like programmatic display where brands have always had flexibility to explore how text, imagery, and animation can come together to tell a story.

So, what constitutes a legible headline? How does headline legibility impact ad performance?

At, headline legibility is a function of both the type size of an ad’s headline and the amount of words in that headline. Type needs to be large enough to read but should contain enough information to be compelling enough to make you click. So how do you reconcile these factors when writing a great headline? 

To answer this question, we placed ads into three different groups based on the amount of type they contained—averaging 35% of the frame per word for high type coverage, 15% of the frame per word for medium, and 5% of the frame per word for low. We then analyzed the performance of each group, measured by click-through rate, in combination with the length of the headlines themselves, ranging from one word to 15. What did the data tell us?

Short headlines in large type…

…outperform loooooooooooooooooonger headlines with smaller type.

In fact, shorter headlines are more impactful than longer ones overall, no matter what the type size, but performance dips as headlines increase in word count. 

As headlines increase in length, the negative impact of that length is amplified by a larger font. So, if a headline has to be long, mitigate the damage by keeping it at a conversational size (and not at a YELLING one) that can distract from other creative elements like imagery and calls-to-action. Otherwise, keep your font size large, about 35% of the frame per word, with just a few words per frame. With premium creative, you can explore advanced uses of animation and imagery to make those few words really shine. 

Footnote for the Analytics Techies

Our model was fitted to variant-level data from April 2020 - April 2021 and filtered to exclude extreme CTRs (>2%) and variants with low serving (IMPRESSIONS < 1000).
To group fonts by size, we used the following measures: High font size = avg 35% of frame per word; mid font size = avg 15% of frame per word; low font size = avg 5% of frame per word.
The data found a significant positive main effect for font size (p < 0.01) and a significant negative interaction of font size together with the number of words in the headline (p<0.01).

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