Is Yoast’s Readability Metric Important for On-Page SEO?

Copywriting SEO

I review Yoast’s readability feature, and break down what works and what doesn’t. I also clarify whether a red light for Readability affects SEO.

Don’t have time to read my full review of Yoast SEO’s readability analysis?  Skip to the verdict instead.

May 2021 Update

Recently, a Yoast representative reached out to me about this article.  2021 marks the fifth anniversary of the readability plugin, and Yoast believe it’s improved a lot since this article was originally published in 2019.  They asked me take another look, and, in the interests of fairness, I’ve done so, although none of my opinions have really changed.

Before you dive in, please note that this is a review of the readability feature of Yoast’s WordPress plugin – I’m not reviewing the rest of the plugin (which is actually pretty useful).

If you work in digital marketing, you’ve probably heard of or used Yoast SEO, WordPress’s leading SEO plug-in. The plug-in’s ‘traffic-light’ system has two sections: SEO analysis, and readability analysis.

The first part essentially checks whether your on-page SEO is up to scratch, while the second part measures the readability of your content/copy using a variety of tests. In this post, I’m going to review the readability analysis, because I think it – along with other automated writing improvement services – not only encourages laziness among writers, but also rewards inferior writing.

Readability Criteria

Yoast’s readability analysis, according to their website, uses six different checks. These are:

  • Transition words
  • Sentence beginnings/consecutive sentences
  • Flesch reading ease
  • Paragraph length
  • Sentence length
  • Passive voice

​I’ve also seen other checks that are not listed here appear when I’ve been editing content, like ‘Subheading distribution’. You can read the exact criteria for each check on Yoast’s website, but, in essence, the analysis encourages short sentences with a variety of structures, short paragraphs, use of active voice, and one- to two-syllable words.

On the surface, this isn’t a bad thing. If someone who isn’t used to writing starts trying to create complex copy and use big words, chances are they’re going to produce something that’s very difficult to read. That said, it’s also quite limiting. I’ll break down each check and explain why.

1. Transition Words

​It almost goes without saying that transition words and phrases can be useful. They add a smooth, conversational flow to your writing, and help readers navigate related sentences.

When writing content, a strong helping of transition words can be useful. That said, they’re situational. When you’re writing certain types of copy, transition words can detract from the way the sentences impact the reader, lessening the effect you’re trying to create.

2. Consecutive Sentences

​Yoast hits the nail on the head with this one. Failing to have a diversity of sentence structures is probably one of the biggest flaws fledgling writers have. It’s a guaranteed way to bore audiences and disengage readers.

3. Flesch Reading Ease

The use of Flesch Reading Ease as a measure for readability is my biggest problem with the readability analysis. The way the Flesch test functions is by assigning sentences a score which correlates with a school level, as shown below.

Score School Level Notes
100 – 90 5th Grade Very easy to read. Easily understood by an average 11-year-old student.
90 – 80 6th Grade Easy to read. Conversational English for consumers.
80 – 70 7th Grade Fairly easy to read.
70 – 60 8th and 9th Grade Plain English. Easily understood by 13- to 15-year-old students.
60 – 50 10th to 12th Grade Fairly difficult to read.
50 – 30 College Difficult to read.
30 – 0 College Graduates Very difficult to read. Best understood by university graduates.


The problem stems from the fact that polysyllabic words are the key determining factor. If you have lots of small words (like this), you will get a high score. The sentence you just read, for example, scores 100, because it uses monosyllabic words. As soon as you start discussing concepts that require larger words for clarity, using industry jargon, using polysyllabic nouns, and so on, your Flesch score plummets.

I often talk about how ‘simple is best’ when it comes to copy, but, as always, that’s situational. Content probably shouldn’t be receiving between 60 – 100 unless you’re writing an instructional guide or how-to article, and copy sometimes benefits from the use of more refined language, particularly if you’re targeting an educated market.

Here’s Yoast’s take on reading ease.

If you do not use too many difficult words and keep your sentences short, the check will pass. That means you will get a green bullet if your text’s reading ease score is higher than 60. Why this number? Because, for web copy, reading ease of 60-70 is considered acceptable. Translated into simpler terms means that a 13-15-year-old should easily understand a good web text.

Here’s my question: why?  Why should your copy or your content be written so 13–15-year-olds can understand it easily?  Unless you’re selling to that market, what a 13–15-year-old can or cannot read on your website is completely irrelevant.

The goal of all marketing is to communicate with your audience.  If that audience is educated with a high degree of assumed knowledge, then you should be looking for the most effective way to talk to them – and, yes, very often that involves using big words that have complex meanings.

I’m not advocating for bloated or overcomplicated copy.  Not at all.  But making massive generalisations in marketing (‘all web copy should have a reading ease of X’) is never a good idea, especially when that generalisation is grounded in bad logic.

4. Paragraph Length

​Paragraph length is definitely important, especially for authors who aren’t used to writing for the web. Reading massive chunks of text on a desktop is painful, but, on a mobile, even worse. I’d probably recommend between 50 and 100 words per paragraph, but it depends entirely on the context. Sometimes single-line paragraphs are useful for driving home important information or breaking up different concepts.

5. Sentence Length

Sentence length, like everything else on the analysis, is measured in percentages. So, if you only have one sentence on the page, and it’s extremely long, you’ll receive a terrible score; if you add a couple of shorter ones, it’ll balance out. While checking sentence length is important, it’s even more imperative that your writing flows properly. It’s no good having a great sentence length score if your writing is choppy and awkward. Moreover, this doesn’t account for the use of semi-colons, which act as a break between conjoined ideas and are less definitive than a period. Again, this is pretty situational.

6. Passive Voice

The castigation of passive voice is my other major problem with Yoast’s readability analysis. If you don’t know the difference between active and passive voice, have a quick read of this article.  Essentially, passive voice places emphasis on the action rather than the subject. You’re probably thinking, “why is that a bad thing?”

Well, it’s not – different situations require different uses of active and passive. For example, use of the passive voice can avoid placing blame (“xyz happened” rather than “Mr. X did xyz”), can sound more authoritative (“the department can be contacted” versus “you can contact the department”) or just emphasise action over subject (“The market was impacted by X” versus “X impacted the market”).

Obviously, the active voice has its place, but condemning the passive voice (particularly when the readability tool is designed for copywriting) seems slightly strange. I’m not sure how strict the tool is, but it’s certainly not desirable to always avoid the passive voice.

7. Subheading Distribution

​Subheading distribution isn’t officially on the Yoast website, but, as I said, I’ve seen it appear when using the analysis, and it’s definitely something to take note of.

Subheadings often aren’t used in traditional articles and academic essays, but they’re incredibly useful for digital content. Aside from the SEO benefits of semantically correct heading tags, headings are easy places to insert keywords, they help break up the text (meaning you don’t have to skilfully segue into new topics), and they make it easy for skim-readers to find the content they’re looking for. So, yes, subheadings are important, and, yes, you should use them where possible.

Does Readability Affect SEO?

So does readability impact SEO? It’s a fair question, particularly if you’re looking at a red frowny-face on your WordPress site and wondering if Google is going to slap you with a ranking penalty.

The answer: not as far as anybody knows. Google doesn’t care about readability, or, at least, not directly. Obviously, better copy means better UX, which in turn creates return visitors and improves the likelihood of being backlinked, but there’s no direct correlate between readability and SEO.

Yoast CEO Marieke van de Rakt actually wrote an article about this, which is worth addressing.  She makes a number of points like:

  • Well-written copy improves UX
  • Search engines mimic humans (referencing Hummingbird’s semantic search)
  • Readability is important for voice search

She also offers a few tips for better writing.

Everything in that article is basically correct.  As a copywriter with a background in creative writing, I fully appreciate the importance of excellent writing for both reader comprehension and satisfaction.  And, of course, we know how important semantic keywords have become, and that NLP (natural language processing) is the way of the future.

Does Yoast’s readability analysis help with any of this?  Not really.  Not unless you’re someone who struggles with writing already.

Why?  Because of how SEO currently functions.  Longer, more comprehensive content has more naturally occurring keywords, has lower bounce rates and satisfies user intent better.  The more comprehensively a topic is covered, the further you, the writer, will have to move away from simple sentences and monosyllabic words.  It’s not realistically possible to consistently cover complex ideas and still get a perfect Yoast readability score.

That said, I do agree that voice search and attempts to get in the featured snippet box benefit from very simply, straightforward sentences.  A question like “What is a copywriter?” would best be answered with 1-2 simple sentences if you were trying for voice search/featured snippet results, even if you elaborated further on in that same blog post.

Interestingly, Wikipedia has the featured snippet spot for “What is a copywriter?”, and their snippet looks like this:

Copywriting is the act or occupation of writing text for the purpose of advertising or other forms of marketing. The product, called copy, is written content that aims to increase brand awareness and ultimately persuade a person or group to take a particular action.

There are a huge number of articles addressing that exact question, and most are probably written by talented copywriters. Yet Wikipedia claimed the featured snippet – and, according to Yoast’s readability analysis, that snippet isn’t considered readable.

It gives it a Flesch score of 38.4, says 50% of its sentences contain passive voice, and says 50% of the sentences are too long.  But Google thinks that, out of every single definition out there, Wikipedia’s is the one that most accurately satisfies search intent.  Wikipedia isn’t even the first SERP result for “What is copywriting?” – it’s the fourth.

Why?  Well, I think it’s because the three websites that rank ahead of it give less accurate definitions, even though their writing is easier to read.

Articulate Marketing:

A copywriter is someone who writes for the internet. They create informative content for businesses that is designed to guide the reader’s own research.

This isn’t correct (at all).  Copywriters definitely don’t just write for websites – there were copywriters long before there was Internet.  Copy also isn’t content – they serve very different purposes.

Kopywriting Kourse:

Copywriting is re-arranging words to make things sell better. It is a text form of salesmanship. But there’s a lot more to it than that.

This is too simplistic, although it is technically correct – they go into detail further down the blog post, but don’t have a concise, accurate definition in one place.


Copywriting is the process of writing advertising promotional materials. Copywriters are responsible for the text on brochures, billboards, websites, emails, advertisements, catalogs, and more.

I don’t mind AWAI’s definition.  It’s technically correct, but lacks the comprehensiveness of Wikipedia’s definition – their second sentence gives examples rather than further defining the word.

This is just one example, but I think it illustrates that readability has virtually no impact at all on rankings.  Even in situations like voice search and obtaining featured snippets – where simpler wording is better – comprehensiveness and accuracy trumps readability.

Testing the Theory

To test my theory that Yoast’s readability analysis doesn’t correlate with higher rankings, I inputted the text from the first SERP result for 7 different search terms into a blank WordPress page, and checked their Yoast readability scores.

Search Phrase Website Readability Score
What is content marketing? Bad
Elephant Bad
How to cook eggs Good
Best hotels london
(second result, first was TripAdvisor) Okay
How to debug javascript Good
Statue of liberty Bad
Setting the iso canon Good

You can see the Yoast readability scores fluctuate dependent on search intent.  ‘How to’ queries have better readability scores (as I explained earlier).  ‘What is’ queries have worse readability scores, because they’re so much more complex.  There’s no evidence to indicate that readability in any way impacts SEO – rather, victory goes to the pages with:

  • High DA (domain authority)
  • Comprehensive content
  • Content that addresses search intent

Getting a green light on Yoast’s readability analysis isn’t a bad thing, by any means.  It doesn’t, however, impact SEO, nor does a green light actually mean your copy/content is any good.  Don’t be verbose, but, if you need to use big words or complex sentences, go for it.  That green light is a red herring.

The Verdict

Yoast’s readability analysis is far from useless, but it’s not perfect either. It has a number of useful checks, and could be helpful for people who aren’t used to writing. That said, unless you’re writing copy designed to be absorbed by pretty much everyone (on government sites, for example), I’d ignore the Flesch score.

Keep your eye on overuse of passive voice, but also take those results with a grain of salt, because passive voice definitely has its place. The best solution is to take the time to become better at writing, or hire a trained copywriter. It doesn’t matter how readable your content is if it’s boring, dumbed-down, or confusingly organised. Overall, I’d say the readability analysis is situationally useful – however, it’s important to realise the distinction between readability as a metric and good writing, because there’s a world of difference.

If you’re not a confident writer or you’re short on time, check out our copywriting and content creation services. If it involves putting words to paper, we’re here to help.

By Duncan Croker

Duncan is a copywriter with a background in editing and storytelling. He loves collaborating with brands big and small, and thrives on the challenges of hard marketing.

One comment on “Is Yoast’s Readability Metric Important for On-Page SEO?”

I have been struggling with Yoast Readability for a while! I tend to write in the passive voice, and Yoast pretty much HATES everything that I write. I am an excellent communicator, but I don’t seem to have English composition skills, although I am working on it. The problem is that I DON’T want to be penalized by Google. Thank you for an EXCELLENT article!!!

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