Comparison

Flashside vs Underline

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

Head to head
About

Flashside

This app uses spaced repetition to help you learn anything, from vocabulary to exam questions. It creates a personalized study plan based on your available time and exam dates, adapting to your progress. Study offline with rich media support and track your learning visually.

Highlights
  • Spaced repetition learning
  • AI-powered study planning
  • Exam preparation mode
  • Customizable flashcards with rich media
  • Offline study capabilities
  • Progress tracking and memory charts
  • Import and share decks
Features
Read full description

Flashside is the flashcard app that plans your learning for you. Make cards for anything — vocabulary, kanji, anatomy, exam questions — and spaced repetition brings each one back at the moment you are about to forget it: after minutes while it is new, then days, then weeks. A few focused minutes a day beat hours of cramming. YOUR PLAN FROM ONE NUMBER Tell Flashside the minutes you have a day and, if you have one, the exam date. It sets the pace, says plainly whether the date is within reach, and every grade button shows when the card will come back. Free for everyone. EXAM PREPARATION • Exam mode: in the last weeks before the date, the deck is drilled until it holds • Quizzes from your own cards, written by hand or generated by AI (Plus); the result keeps your answer beside the right one • A memory chart for every collection: how much you would recall today, the last 30 days, and where it goes if you stop • Start a collection over for the next exam without losing its history PERSONALIZED LEARNING AI A coach that plans your days, fixes the cards you keep failing and quizzes you before the exam — it never answers for you. • New words come back after a few minutes, and the pause adapts to how well they stick for you • Card doctor: when a card will not stick, it suggests better ways to write it. You pick the fix, or none (Plus) • A coach card every Monday with what to change this week, and why you missed a card you were sure of (Plus) • Reminders that move to the hour you actually study Remembering stays your job, because that is the part that makes you learn. EVERYTHING ON YOUR DEVICE Your cards, collections and progress live on your phone. Study on a plane, in the subway, off the grid — no account, no connection, no waiting. Sign in with one tap when you want sync, sharing or the web app at flashside.app, never before. CARDS THE WAY YOU THINK • Rich text, colors, images and audio on both sides, read aloud on request • Flip the direction, shuffle, hold the card to take back an answer • Import ready-made decks from CSV or Excel, paste a list with your own separators, or photograph a page (Plus) • Share whole collections with classmates and friends • Search every card and study from the one you found EARN IT Every session ends on a reward screen: your score, last time's, your streak, and now and then a badge sweeping in. Dozens of badges are hiding in Flashside — for showing up, flawless sessions, mastered collections and a few things you will have to discover. MAKE IT YOURS • Five color themes, each in light and dark • Clean, fast, distraction-free design • Available in 18 languages LEARNING STAYS FREE Writing and studying cards, the plan, the memory chart, exam mode, syncing and sharing are free, and your cards always belong to you. Plus is for learners with a date: an exam in a few weeks, a language test, a semester to pass. No ads. Learning is never capped. Plus is only the part that costs us money to run. The Plus extras: natural read-aloud voices, translation, AI-written quizzes, the card doctor, importing from a picture and the coach's explanations. Each one is clearly marked, and nothing is charged without your consent. Flashside Plus: €19.99 a year, every device and the web · Quizlet Plus Unlimited: €44.99 a year, ads on the free tier · AnkiMobile: $24.99 once, iOS only. Prices as of October 2026. Whether you are learning a language, prepping for med school, collecting kanji or just tired of forgetting names — start with one card today. Your future self will thank you at review time. Terms of Use (EULA): https://flashside.app/eula Privacy Policy: https://flashside.app/privacy-policy

About

Underline

Features
Read full description

Learning languages in 5 steps: 1. You download the app for free 2. We introduce you to the Underline world 3. You add your own flashcards or use our browser plugin 4. You remember words by practicing with one of our learning modes 5. You know the language you learn! Advantages of learning languages with Underline: • You receive flashcards for learning from us or you build your own unique base yourself using our browser add-on • You get access to suggested words based on the words you translate. • You choose the learning mode that suits you best: - viewing flashcards, - written translation of words, - typing words by ear, - quizzes (choice of answers) - mixed mode. • You listen to the vocabulary as it is pronounced, thanks to which you remember them faster • You use a handy translator that you can use as a source of new flashcards from your phone • You can choose from a system of intelligent repetitions or folders to organize the level of knowledge of your words • You set the frequency of learning (your goal) with reminders about it • You monitor the progress in your profile - thanks to this you know how your level of language proficiency is improving If… • You learn English from scratch • Are you looking for a perfect solution at work • Your technical or business language needs "upgrade" • You are preparing for your high school diploma or other exams • You are going to go abroad, but you prefer to expand your vocabulary beforehand • You have many friends from other countries that you want to chat with freely … Underline will be your best choice! In our application for learning English or another language, you can use the flashcards received from us or build your own unique database. That is why Underline is perfect for: • for beginners • for intermediate • for advanced By combining two compatible tools - a mobile application and a browser plug (extension), Underline combines the process of searching, translating, saving, and learning words, which allows you to learn the vocabulary you really need. In addition to English, we also have languages such as: • Spanish • Ukrainian • German • French • Japanese • Korean • Chinese and many others. Underline works best with our browser plugin, so if you want to learn a personalized vocabulary, feel free to download it! Our extension works for Chrome, Opera and Microsoft Edge:https://chrome.google.com/webstore/detail/underline/ogdfpjfkomoeoodbemmkloabcjkmmbol Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Flashside4 screens
Underline4 screens

Verdict

The call

The clearest difference is in-app purchases: Underline at none against Flashside's 2. Underline also leads on iOS requirement (10.0 vs 18.6). Flashside's advantage is update cadence (every 3 weeks vs every 2 months). On price, ads and device support 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

Both are free to download. Flashside sells 2 in-app purchases, starting at $2.99 per month. Underline asks for nothing beyond the download.

UpkeepUpdate frequency

Flashside ships an update every 3 weeks, Underline every 2 months. The most recent releases landed on November 3, 2026 and October 27, 2026 respectively.

Scorecard3 real differences · 7 level
Flashside versus Underline: the parameters behind the verdict, then further details
ParameterFlashsideUnderline
PriceFreeFree
Rating5.0 (2 ratings) — better—
Positive reviews100.0% of reviews—
Number of ratings2 — better—
Update frequencyEvery 3 weeks — betterEvery 2 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFreemium—
DevicesiPhone, iPadiPhone, iPod
Requires iOS18.610.0 — better
Further details — not scored
Size65 MB40 MB
Age rating4+4+
DeveloperCQUELLE GmbHDamian Skoneczny

In-app purchases

2 purchases

Flashside

Subscriptions2
  • Flashside Plus Monthly$2.991 Month
  • Flashside Plus Yearly$17.991 Year
None

Underline

No in-app purchases

Questions

Is Flashside free?
Flashside is free to download, with in-app purchases available.
Is Underline free?
Underline is free to download, with no in-app purchases.
Do Flashside or Underline have ads?
Neither Flashside nor Underline shows ads.
Which is updated more often, Flashside or Underline?
Flashside ships an update every 3 weeks, and Underline every 2 months. Most recently, Flashside was updated on November 3, 2026 and Underline on October 27, 2026.

Other comparisons