Hydro-etch AI

What is hydrogen etching?

HydroCut is a card-based note-taking and memory-aiding tool developed by Beijing HydroFlow Network Technology Co., Ltd.

It organizes information into sets of cards, and uses flashcards, quizzes, and spaced repetition to help users reinforce their knowledge.

Core functions

Card notes and card sets

Each card set functions as a small knowledge base, consisting of multiple cards that deal with the same topic.

• A single card contains only one piece of knowledge that is understandable and easy to recall.
• The title should state the question or concept, while the body should contain brief answers along with any necessary examples.
• The main topics are divided into multiple sets of cards, so as to prevent a single card from containing the content of an entire chapter.
• Use tags and searches to quickly find relevant cards.
• Regularly merge duplicate content and mark outdated information.

AI flashcards and quizzes

Hydrogen can automatically generate flashcards, fill-in-the-blank questions, key points, mnemonics, and quiz questions from notes.

• Flashcards are suitable for active recall; the answers should not be shown directly in the questions.
• It is suitable for terms, formulas, and fixed expressions, but not for complex arguments.
• Memory aids should remain accurate; facts must not be distorted for the sake of rhyme.
• AI quizzes are suitable for checking comprehension, but the questions and answers may be incorrect.
• After completing the quiz, one should return to the original material to identify the reasons for the errors.

Spaced repetition

The system schedules the next learning session based on the user’s feedback regarding their mastery of the cards.

1. When in learning mode, the system displays the cards that need to be reviewed at the moment.
2. First, try to recall the answer, then check the back of the card or the detailed information.
3. If you are unsure or answer incorrectly, choose to continue learning; do not claim to have mastered it.
4. Once the response becomes stable, select “Already mastered”; the system will then increase the interval between reviews.
5. Regularly check the statistics to identify topics that are repeatedly forgotten over time.

Spaced repetition can improve the rhythm of review, but it cannot replace understanding, practice, and the application of knowledge.

Importing and organizing data

HydrogenNote supports importing WeChat Reading notes and Anki flashcards, thereby reducing the need for repetitive organization tasks.

• WeChat Reading: Converts highlights and notes into cards that can be reviewed.
• Anki: When migrating existing flashcards, check that the fields and formats match.
• Images, recordings, and attachments: used to supplement example images, pronunciations, and original materials.
• After importing, delete excerpts without context and add the source along with your own explanations.
• Important data should be backed up separately to avoid storing it solely in one cloud service.

Hydro Engraving Tutorial

1. Register for an account and create your first card set, choosing a clear learning topic.
2. Break down textbooks, notes, or excerpts into short, separate cards.
3. Generate candidate content using automatic highlighting and blanking, followed by manual correction.
4. Generate flashcards and quizzes, and remove questions with non-unique answers or ambiguous wording.
5. Every day, enter learning mode: first recall the information and then check the answers.
6. Choose to continue learning or indicate that you have mastered it, based on your actual level of understanding.
7. Every week, organize the duplicate cards, incorrect answers, and outdated materials.
8. Export or back up important knowledge bases and attachments on a monthly basis.

Suitable for which learning tasks

• Language learning: words, fixed expressions, example sentences, and pronunciation.
• Exam preparation: concepts, formulas, regulations, and common error points.
• Professional studies: knowledge in medicine, law, engineering, and qualifying examinations.
• Reading accumulation: book excerpts, perspectives, counterexamples, and personal reflections.
• Work knowledge base: processes, product information, and common questions.
• Inspiration management: Record random ideas and review them regularly.

Comparison of member prices and features

The following is the information displayed on the pricing page as of August 30, 2026; the total cost for the entire cycle must be checked on the purchase page.

The page currently shows a 25% discount during the school opening season; the starting price applies to a specific purchasing period only, and it does not mean that the same price will be valid for all periods.

Prices, promotions, frequencies, and benefits may change; the final details will be those displayed on the purchase page, the settlement page after logging in, as well as the current agreement.

Refund and expiration rules

• After making a purchase via WeChat, a refund can be requested within 7 days of the purchase, following the instructions provided in the official email.
• Account information must be provided at the time of application; the actual eligibility is determined by the order and the processing results.
• The data remains intact even after the premium version expires.
• Accounts that have reached their expiration date can continue to be used under the limits of the free version, and they are no longer entitled to the member privileges.
• Both the free version and the premium version allow unlimited access to card sets shared by others.

Supported platforms

Data, APIs, and open-source status

• Data synchronization: The official website explains data synchronization across multiple devices.
• Data protection: Officials state that isolation, encryption, and access control are employed.
• API: As of the time of verification, no public developer API documentation was found.
• SDK: No verifiable official SDK has been found.
• Open source: No complete source code for the product or an official open source license was found.

The use of third-party SDKs by clients does not mean that H2O provides its product SDKs to developers, nor does it imply that the services can be deployed privately.

Usage restrictions and precautions

• Cards and questions generated by AI may contain factual errors or may not have a single correct answer.
• Community card sets are created by other users; it is necessary to check the quality of their content before using them.
• When sharing book excerpts, it is necessary to comply with copyright and fair use rules.
• Do not record passwords, keys, identification documents, or any other sensitive information that has not been masked.
• Spaced repetition is suitable for memorization, but it does not replace deep understanding and practical practice.

Frequently Asked Questions

What can hydrogen etching mainly do?

It organizes notes into card sets and uses flashcards, AI quizzes, and spaced repetition to aid memory.

What are the limitations of the free version of 氢刻?

A maximum of 3 card sets can be created, with up to 30 cards in each set; the recycle bin retains items for 7 days.

How much is the advanced version of HydroCut?

The public page shows that the cost starts as low as 3.9 yuan per month; the total amount for a specific period needs to be checked on the purchase page.

What are the differences between the AI Professional version and the Advanced version?

The premium version offers 200 uses of the AI functions per month, while the professional AI version provides unlimited access to these functions.

Does Hydrogen Note support importing from Anki?

It supports importing Anki flashcards, as well as converting notes and ideas from WeChat Reading into flashcards.

Will the data be lost when the membership expires?

No, according to the official statements, all data will be retained, but the account will continue to function with the features available in the free version.

Does Hydrogen provide APIs or open-source code?

As of the time of verification, no public APIs, official SDKs, complete source code, or open licenses were found.