In our previous post, we explained why Type Fast takes a personalized approach to typing instruction. Now we will dive into the technical details of how that personalization actually works.
How New Keys Are Introduced
When you are ready for new keys, Type Fast adds them in order of how frequently they appear in English text. The sequence begins with E, which is the most common letter in English, followed by T, A, O, I, N, S, H, R, and so on, ending with Z, which is the least common.
This frequency-based ordering serves an important purpose. By learning high-frequency letters first, you can start typing real English words much sooner in your learning journey. This makes practice more engaging because you are typing meaningful text rather than random letter combinations, and it reinforces the natural patterns that appear in everyday typing.
The system will not add a new key until you meet two important criteria. First, all of your current keys must reach eighty-five percent confidence, which we will explain in detail shortly. Second, each key needs at least five recorded attempts to ensure that the performance data is statistically reliable. These requirements prevent the system from promoting you too quickly based on a few lucky keystrokes. We would rather you spend extra time solidifying your foundation than rush ahead and develop shaky habits.
The Focus Key System
At any moment during your practice, your weakest key becomes what we call the focus key. The text generator then ensures that eighty to one hundred percent of the words in your practice session contain this specific key.
For example, if you struggle with the letter R, you might see practice text like “red river road rather render rare reader.” This concentrated exposure accelerates your improvement on your weakest link by giving you far more practice with that key than you would get from random text.
Once your focus key improves enough that it is no longer your weakest, the system automatically shifts focus to whatever key is now holding you back. This creates a self-balancing system where your practice time is always allocated to wherever it will do the most good.
Understanding Confidence Scores
Confidence is the core metric that Type Fast uses to measure your proficiency with each key. It represents how close you are to your target typing speed for that specific key.
The calculation is straightforward. We divide your target time per keystroke by your actual average time. If your target is two hundred milliseconds per keystroke and you average two hundred milliseconds, your confidence is one hundred percent. If you average four hundred milliseconds, which is twice as slow as your target, your confidence is fifty percent.
However, raw timing data can be noisy. One slow keystroke because you hesitated or got distracted should not dramatically change your score. To handle this, Type Fast uses a technique called exponential smoothing. Each new keystroke only contributes ten percent to your running average, while your previous average contributes ninety percent. This creates a stable and reliable measure that gradually adjusts as your true speed changes while filtering out random outliers that do not reflect your actual ability.
Based on these confidence scores, each key falls into one of three categories. Keys below sixty percent confidence need focus and will become your focus key to get extra practice. Keys between sixty and eighty-five percent are in the practicing zone, meaning you are making progress but are not yet consistent. Keys at eighty-five percent or above are considered mastered, indicating that you are typing them at or above your target speed reliably.
When all of your current keys reach the eighty-five percent mastery threshold, the system introduces the next key in the frequency sequence. This ensures that you have a solid foundation before adding new complexity.
How Practice Text Is Generated
Type Fast does not use pre-written practice sentences. Every lesson is generated dynamically based on your current key set, which ensures that you are never practicing keys you have not learned yet.
The generation process follows a careful priority system designed to give you the most natural and effective practice text possible.
The system first attempts to filter real English words from a database of several hundred common words, keeping only words that can be spelled entirely with your current keys. With just the home row keys, for example, valid words include “all,” “fall,” “glad,” “hall,” “salad,” and “flask.”
If fewer than twenty words pass this filter, the system adds words from an extended vocabulary list containing several hundred more advanced words. This expands the pool while still ensuring every word uses only keys you have learned.
If the system still has fewer than ten valid words, it begins generating what we call pseudo-words. These are pronounceable combinations built from common English letter pairs, known as bigrams, such as “th,” “er,” “in,” and “an.” These pseudo-words are not real English words, but they feel natural to type because they follow the same letter patterns that appear in real text.
As a final fallback for situations with very limited key sets, the system creates simple key combinations to ensure you always have something to practice.
After building the word pool, the generator applies focus key boosting if you have a focus key. When enough words contain the focus key, the system uses only those words, ensuring that every word in your practice targets your weakness. When fewer focus words are available, at least eighty percent of the selected words will still contain your focus key, ensuring concentrated practice where you need it most.
The result of this multi-stage process is readable, pronounceable text that feels natural while targeting exactly what you need to practice.
Why Real Words Matter
We put significant effort into using real words whenever possible because typing random letter combinations, while it does build basic finger coordination, misses an important aspect of how real typing works.
When you type the word “the” thousands of times across your practice sessions, your brain gradually stops processing it as three separate keystrokes. It becomes one fluid motion, a single chunk in your muscle memory. Common words and letter combinations become these automatic chunks that you execute without conscious thought.
By using real words from the very beginning of your learning journey, Type Fast helps you build these chunks naturally. You are not just learning where keys are located. You are learning how keys flow together in the patterns that make up actual English text.
In the next post, we will cover how to track your progress and share principles for effective practice.