MathForge vs DuoSub
Price, ratings, monetisation and update history for both apps, side by side ā with what reviewers say about each.
MathForge
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MathForge: Skill Quest transforms math practice into an interactive progression game. Begin with a placement trial, enter skill-based arenas, solve increasingly challenging problems, and battle bosses to prove your mastery. Earn XP, unlock rewards, complete missions, and strengthen the skills that need the most practice. MathForge includes practice across arithmetic, fractions, decimals, algebra, geometry, probability, logic, and introductory SAT-style math. Features: ⢠Placement Trial that helps determine your starting level ⢠Skill-based math arenas with increasing difficulty ⢠Boss battles that test what you have learned ⢠XP, ranks, achievements, missions, and rewards ⢠Daily practice goals and progress tracking ⢠Mistake review and weakness-focused practice ⢠Light and dark appearance options ⢠Optional soundtrack and mobile-friendly controls ⢠No account or login required MathForge is designed to make consistent math practice feel more motivating, focused, and rewarding.
DuoSub
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Watch YouTube in two languages at once. DuoSub plays a video with two subtitle lines: the original line, and your own language right underneath it. Nothing to download, no subtitle files to hunt for, no settings to fight with. HOW IT WORKS 1. Bring in a video ā paste a link, share it from the YouTube app, or find it in the built-in Browse tab. 2. Choose the language for the second line. 3. Press play. Both lines run with the video, word by word. WHAT YOU GET ⢠Dual subtitles ā the original on top, your translation below, always in sync. ⢠90 languages for the translated line, from Vietnamese, Spanish and Japanese to Arabic, Hindi and Ukrainian. ⢠Karaoke highlighting that frames the word being spoken, so you never lose your place. ⢠A full transcript that scrolls along with the video ā tap any line to jump to that moment. ⢠Your subtitles, your way: text size, a colour for each line, karaoke on or off ā adjustable without leaving fullscreen. ⢠A real player: drag the seek bar, tap to pause, swipe for brightness and volume, hold for 2x, lock the screen. ⢠A library that keeps every video you add, with its subtitles saved on your device so replays start instantly. ⢠The app itself in 12 languages, switchable any time without a restart. WHO IT'S FOR People learning a language from real videos instead of textbook audio. Listeners who want an hour-long podcast to stop being a wall of sound. Students following courses recorded in another language. Anyone reading foreign news and documentaries as they play. DUOSUB PRO Free: translate up to 3 new videos a day. Videos that have already been translated open for free and don't use up your daily count. Pro: unlimited translation, every language, every day. ⢠1 month ā 149,000 ⫠⢠3 months ā 299,000 ⫠⢠12 months ā 799,000 ā« Prices shown are for Vietnam; your local price appears on the purchase screen before you pay. Payment is charged to your Apple ID at confirmation of purchase. The subscription renews automatically unless it is turned off at least 24 hours before the end of the current period. Manage or cancel any time in your Apple ID settings. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://duosub-1ae27.web.app/privacy GOOD TO KNOW DuoSub works with videos that have captions available. Videos play through YouTube's own player ā DuoSub does not download or store video. DuoSub is an independent app and is not affiliated with, endorsed by or sponsored by YouTube or Google.
Screenshots
Verdict
The clearest difference is in-app purchases: MathForge at none against DuoSub's 3. MathForge also leads on ads (none vs shown). On price, update cadence, device support and iOS requirement there is nothing between them.
Scored on Price Ā· Rating Ā· Positive reviews Ā· Number of ratings Ā· Update frequency Ā· Ads Ā· In-app purchases Ā· Monetization Ā· Best chart rank Ā· Devices Ā· Requires iOS
Both are free to download. DuoSub sells 3 in-app purchases, starting at $4.99 per month. MathForge asks for nothing beyond the download.
MathForge ships an update every 3 days, DuoSub every 5 days. The most recent releases landed on October 8, 2026 and October 1, 2026 respectively.
| Parameter | MathForge | DuoSub |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 3 days ā better | Every 5 days |
| Ads | No ā better | Yes |
| In-app purchases | No ā better | Yes |
| Devices | iPhone, iPad | iPhone, iPad |
| Requires iOS | 18.6 | 17.0 ā better |
| Further details ā not scored | ||
| Size | 5 MB | 12 MB |
| Age rating | 4+ | 17+ |
| Developer | Anil Sharma | Vui Nguyen |
In-app purchases
MathForge
No in-app purchases
DuoSub
- DuoSub Pro - 1 Month$4.991 Month
- DuoSub Pro - 3 Months$9.993 Months
- DuoSub Pro - 1 Year$24.991 Year









