Exploring Readability Score solutions for developers: Libraries and APIs

In this blog, we will talk about some of the solutions that developers can use for calculating the Readability Scores in their applications. This includes open source libraries and APIs. For each of the two, we will have a look at some of the available options and discuss their pros and cons.
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Sohail Pathan
Last updated on November 30, 2023


In our previous blog, we discussed readability scores and how calculating them can give someone insights into the overall comprehensibility and ease of understanding of any blog, text, or written content.
Quick recap: Readability scores are mathematical formulas that analyze text with the purpose of quantifying how easy or challenging a text is to read. One of the known formulas used to assess the readability of a piece of text, whether it's a sentence or a paragraph, is the Flesch Reading Ease Score.
In this blog, we will talk about some of the solutions that developers can use for calculating the Readability Scores in their applications. This includes open-source libraries and APIs. For each of the two, we will have a look at some of the available options and discuss their pros and cons.

Top Open Source (Free) entity on the market:

We start with open-source libraries: I find these to be super effective for users seeking a more cost-effective engine for small or medium-scale projects. Here is the list of some open-source libraries available:
  1. flesch-kincaid: This is a TypeScript library that calculates the readability of a text according to the Flesch–Kincaid formula.
  2. Whelk-i: This is a Java library that is used to perform Flesch-Kincaid readability tests. It has some easy-to-understand documentation.
  3. Py-readability-metrics: py-readability-metrics is an open-source library available in Python that is actively maintained by the community. One of the advantages is that it lets users check the readability not only for Flesch-Kincaid but with various algorithms and formulas like Gunning Fog, ARI, Dale Chall, SMOG, Space, and more.
This is obviously not a definitive list. Any libraries that we missed? Please let us know.
However, libraries come with certain drawbacks that make their use suboptimal (prefer APIs). Below are some of the main problems I find in libraries.

Cons of Using (Free) Open Source Libraries

Technical Limitation: Libraries are programmatic way and could be suited for medium-scale projects. However, libraries are dependent on the tech stack that a developer is using. For example, fewer robust libraries may be available for Javascript but not for languages like Go or Java.
Maintenance: Libraries can become unusable components if it’s not maintained by the community or providers. Also, it’s important to have backward compatibility support when you update the app for new users/devices or operating systems.
Limited Documentation: Some open-source libraries may need more complete or better-maintained documentation. This can make it difficult for developers to understand how to use the model effectively, leading to frustration and wasted time.
Customization: Open-source libraries provide pre-built and reusable code, but they may not always offer the exact features or behavior desired for a particular use case. It can, after all, be a real pain when a user needs to modify the library's functionality to meet specific requirements or preferences of a software application or system.

Most Popular Cloud APIs

Clearly, libraries have their strengths but there could be scenarios where developers want to avoid the risks of using external libraries, and have a simple and straight forward plug and play solution. Cloud APIs offer exactly that - they enable you to access powerful pre-built services over the network through simple API calls. It’s suitable for those who prefer a more user-friendly approach and dislike complex integration or infrastructure setup. Below are some providers of Readability Score API.
  1. Sapling: Saplings are offered by naming them as Statistic API. For developers, with simple documentation, it also offers language-specific client code in JavaScript and Python.
  2. SEOReviewTools: SEOReviewTools offers a service that quickly calculates the Flesch-Kincaid readability score for any URL. For developers, with simple documentation, it also offers language-specific client code in Python and PHP.
  3. ApyHub: ApyHub provides a Readability Score & Readability Score Documents API that enables users to check the readability of texts and documents seamlessly. Users can simply pass the text, PDF, or Docs and get back a response that includes the overall score, grade level, class of the reader, and more.

Cons of Using Cloud APIs

While there are no major challenges to using cloud APIs, it's good to consider factors like an effective pricing model, well-structured documentation, availability in terms of uptime, and customer support.
Below is a summary of the comparison of the providers:
Provider# Calls (Free)Input FormatFile SizeResponseAPI TestingPricing ( Paid )Throttling
SEOReview ToolsNo Calls in Free PlanHTMLN/AScore, Grade level, Label, Class, Reading time, Speaking time, Character countsN/AStarting from 25 USD / month.N/A
ReadableNo Calls in Free PlanTXT, Docx, PDF, HTMLN/AScore, Grade Level, Label, Class, Reading time, Speaking time, Sentiments RatingTest in PostmanStarting from 24 USD/ Month Custom pricing plan for Enterprises.N/A
SaplingUpto 20 Calls in Free PlanDocx, PDF, HTMLN/AScore, Grade Level, Label, Reading Time, Characters CountInbuilt only text validator.Starting from 25 USD / month.N/A
ApyHubUpto 2M calls in the free planTXT, Docx, PDFs,50 MBScore, Grade Level, Label, Class Label, Reading Time, Speaking time, Characters Count, Words Count, Sentence Count Paragraph CountIn-built API Playground for testing Input.Starting from 10 EUR/month. Custom pricing platfor Enterprises.1 call/s in the free plan
  • N/A - Not found on the company website.

Why choose ApyHub?

ApyHub aims to strike a balance and help developers, team leaders, and engineering managers by seamlessly integrating APIs into their applications. Below are some of the core benefits:
  1. Single Subscription - Not just one but you can access all APIs from ApyHub’s Catalog APIs with a single API Key.
  2. Offerings - All APIs are operated, maintained, and monitored by ApyHub, and data is managed by a single provider.
  3. Documentation: For developers, ApyHub provides rich documentation for each API including the ability to generate client code for 9+ Programming languages and SDK support in NodeJs and Go.
  4. Community Support: ApyHub has its own Discord Server to help developers resolve issues in the quickest possible way.
  5. Availability: ApyHub has served 99.99% of uptime.
Have you tried our ApyHub’s API? Get started here in the API playground.
If you think ApyHub suits your project requirements, let us know here

Next steps….

Ultimately, the Flesch Reading Ease score can assist with creating content that is easy to read and understand, which is important for anyone who wants to communicate their message to their audience effectively. The approach depends on the use case and requirement.
Do you agree with our list of the above API Providers? What do you think is the best watermarking API? Let us know your thoughts in the comments below.
*Disclaimer: This article is for informational purposes only. The opinions expressed are solely based on the research and may vary based on individual experiences and preferences.