R21 vs AVACAST Tx
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
R21
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R21 is a new six-level reading series carefully designed to help young learners develop the skills they’ll need to succeed in the 21st century. Each book covers a range of topics and makes use of the latest Content and Language Integrated Learning (CLIL) methods to ensure they’ll appeal to young children and have a connection to children’s wider studies and experiences. With R21, reading is fun, inspiring as well as informative, and children will not only develop their reading competence but also become a great thinker in the 21st century.
AVACAST Tx
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The AVACAST Tx app provides additional controls and features for users who want to cast or mirror their screens while using AVA OnCollab devices. This app unlocks the full potential of your OnCollab unit, enabling you to collaborate in your workspace or classrooms like never before.
Screenshots
Verdict
The clearest difference is iOS requirement: R21 at 9.0 against AVACAST Tx's 16.0. On price, update cadence, ads and in-app purchases 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
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
Both ship on a similar rhythm, roughly every 3 months. The most recent releases landed on November 2, 2026 and November 4, 2026 respectively.
| Parameter | R21 | AVACAST Tx |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 3 months | Every 3 months |
| Ads | No | No |
| In-app purchases | No | No |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 9.0 — better | 16.0 |
| Further details — not scored | ||
| Size | 114 MB | 25 MB |
| Age rating | 4+ | 4+ |
| Developer | CAVES BOOKS LTD. | 禾麟數碼科技股份有限公司 |
In-app purchases
R21
No in-app purchases
AVACAST Tx
No in-app purchases









