Comparison

Calendar vs Readwise Highlights

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Calendar

Read full description

Supported Languages: German and English With this app you can train your ability to calculate a weekday for any given date. It offers a great variety of training methods. This app also gives you an overview of my method/simplification on how the algorithm works and how you can calculate it in your head.

About

Readwise Highlights

This app helps you retain more of what you read by centralizing and revisiting your highlights from various reading platforms. It uses spaced repetition and active recall techniques to improve memory and offers features like tagging, note-taking, and OCR for physical books.

Highlights
  • Synchronize highlights from multiple platforms
  • Daily review habit via app and email
  • Spaced repetition and active recall
  • Tag, note, and search highlights
  • OCR for paper book highlights
  • Convert highlights to flashcards
Features
Read full description

Readwise helps you get the most out of what you read by making it fun & easy to revisit your highlights from all your favorite reading platforms in one place. Quickly synchronize your highlights from Kindle, Apple Books, Instapaper, Pocket, Medium, Goodreads, and even paper books. Then start building a daily review habit using the app and daily email. By reviewing your highlights every day, you'll retain dramatically more and you'll finally stop forgetting all the details from books you just finished! --- “Readwise is my favorite new service this year. Save highlights from Kindle, Instapaper, and now tweets... one of the best long-term personal learning tools I’ve come across.” — Caleb Hicks “Besides my Kindle, Readwise has been the most influential tech for improving my reading process.” — Blake Reichmann “If you use Kindle or Instapaper or just enjoy keeping and reading highlights, please sign up to Readwise. It will become one of your cherished services.” — Christopher Galtenberg --- ACTUALLY USE YOUR HIGHLIGHTS Highlighting is great, but why bother if you're never going to see any of your highlights again? Readwise makes it easy to quickly liberate all your highlights into one place, ensuring that you'll actually see and use them, including highlights from: • Amazon Kindle • Apple iBooks • Instapaper • Pocket • Medium • Goodreads • Twitter • Physical Books (using OCR) • Manual Input • CSV Upload STOP FORGETTING WHAT YOU READ How often do you finish a book, only to forget the key ideas two weeks later? We don't remember things by just reading them once. Readwise solves this problem using scientifically proven learning techniques called Spaced Repetition and Active Recall. Readwise resurfaces the right highlights at the right times using a daily email and an app. Readwise even makes it possible to convert your best highlights into flashcards for added retention. TAG, NOTE, SEARCH, AND ORGANIZE With your highlights all in one place, Readwise enables you to organize and connect these ideas in new ways. Use search to find a highlight instantly; use tag to organize highlights within your library; use notes to add your own annotations. HIGHLIGHT PAPER BOOKS Readwise also makes it possible to take highlights from your physical books and papers using your phone’s camera. Just snap a pic, highlight with your finger, and have your favorite highlights saved forever. --- If you are not already a Readwise subscriber, you can get started immediately with a 30-day free trial with no credit card upfront. At the end of the trial, you will not be charged unless you choose to subscribe to Readwise Full or Readwise Lite. Price may vary by location. Manage your subscription from your dashboard. --- Support: Check out readwise.io/faq or email us at hello@readwise.io Privacy Policy: https://readwise.io/tos Terms of Service: https://readwise.io/privacy

Screenshots

Calendar2 screens
Readwise Highlights4 screens

Verdict

The call

The clearest difference is price: Readwise Highlights at Free against Calendar's $31.99. Readwise Highlights also leads on update cadence (every 2 weeks vs every 31 months). Calendar's advantage is in-app purchases (none vs 8). On ads, device support and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Readwise Highlights is free to download; Calendar costs $31.99 up front. Readwise Highlights sells 8 in-app purchases, starting at $4.99 per month. Calendar asks for nothing beyond the download.

UpkeepUpdate frequency

Calendar ships an update every 31 months, Readwise Highlights every 2 weeks. The most recent releases landed on October 18, 2026 and October 29, 2026 respectively.

Scorecard3 real differences · 7 level
Calendar versus Readwise Highlights: the parameters behind the verdict, then further details
ParameterCalendarReadwise Highlights
Price$31.99Free — better
Rating—4.8 (1.5K ratings) — better
Positive reviews—69.3% of reviews
Number of ratings—1.5K — better
Update frequencyEvery 31 monthsEvery 2 weeks — better
AdsNoNo
In-app purchasesNo — betterYes
Monetization—Free with in-app purchases
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.615.5 — better
Further details — not scored
Size1 MB112 MB
Age rating4+12+
DeveloperMartin EiseleReadwise, Inc

Bugs and requests

Calendar

Not enough reviews yet to summarise bugs or requests.

Readwise Highlights

Reported bugs

3 issues
  • Frequent app crashes
  • Sync failures with certain accounts
  • Unreliable highlight capture

Requested features

5 requests
  • Add support for more reading apps
  • Improve sync and import capabilities
  • Introduce more customization options
  • Enhance search and organization tools
  • Develop a more intuitive mobile interface

In-app purchases

None

Calendar

No in-app purchases

8 purchases

Readwise Highlights

Subscriptions8
  • Readwise Lite Monthly$4.991 Month
  • Readwise Lite Monthly$6.991 Month
  • Readwise Full Monthly Plan$8.991 Month
Show 5 more
  • Readwise Full Monthly$12.991 Month
  • Readwise Lite Yearly$52.991 Year
  • Readwise Lite Yearly$66.991 Year
  • Readwise Full Yearly$94.991 Year
  • Readwise Full Yearly$119.991 Year

Questions

Is Calendar free?
Calendar costs $31.99, with no in-app purchases.
Is Readwise Highlights free?
Readwise Highlights is free to download, with in-app purchases available.
Do Calendar or Readwise Highlights have ads?
Neither Calendar nor Readwise Highlights shows ads.
Which is updated more often, Calendar or Readwise Highlights?
Calendar ships an update every 31 months, and Readwise Highlights every 2 weeks. Most recently, Calendar was updated on October 18, 2026 and Readwise Highlights on October 29, 2026.

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