When you start paying attention to keyboards, get ready to buy a new one, or want to replace the keycaps on your keyboard, you will quickly encounter a series of unfamiliar yet critical terms: ANSI, ISO, full-size, TKL, 75%, 65%, 60%... Behind these names are two entirely different keyboard layout systems and multiple size specifications designed for different usage scenarios. If you don't figure out the differences in advance, you might end up buying a keyboard whose layout doesn't match your habits, or discover that the keycaps you love simply won't fit your keyboard. This article will systematically introduce the two most common keyboard systems on the market—ANSI (American) and ISO (European/International)—as well as all major size specifications from full-size to 60%, helping you build a complete framework for understanding keyboard layouts.

Before diving into the details, let's clarify two core concepts: first, the "layout system" determines the shape, size, and arrangement of keys (the most intuitive example being the shape of the Enter key); second, the "size specification" determines how many key zones the keyboard retains. The same layout system can have different size specifications—for example, the ANSI system offers full-size, TKL, 75%, and more; and the same size specification will also have different key counts and arrangements between ANSI and ISO. Understanding the intersection of these two dimensions is key to choosing the right keyboard.

1. ANSI (American) Keyboard System

ANSI stands for American National Standards Institute. The keyboard layout it defines is the most widely adopted standard globally, and it is the default system supported by the vast majority of mechanical keyboards, gaming keyboards, and keycap sets. Whether you buy a keyboard in China, North America, or Southeast Asia, chances are you'll get an ANSI layout.

  • Core characteristics: The most distinctive feature of the ANSI layout is the horizontal rectangular Enter key (spanning about two rows in height but 1.5 standard keys in width), and the long Backspace key located directly above it (about 2 standard keys wide). The left Shift key is a standard 2.25u width, and the right Shift key is relatively wide (about 2.75u width). On either side of the spacebar are three 1.25u modifier keys (Ctrl, Win, Alt), arranged neatly and symmetrically.
  • Keycap compatibility: Since ANSI is the market mainstream, almost all third-party keycap sets are designed with ANSI as the baseline. The cross-shaped stem positions on the underside of keycaps also follow the ANSI standard, so the range of options when swapping keycaps is extremely broad, and you'll rarely encounter compatibility issues.
  • Symbols and typing habits: The symbol key positions in the ANSI layout (such as @, ", #, etc.) are designed based on American English. Chinese users who use pinyin input methods layer Chinese input on top of this, and it works perfectly. If you're used to typing English directly on the keyboard, the ANSI layout is also the standard choice for programming and English writing.

The ANSI system covers a complete range of size specifications, from the largest full-size to the smallest 60%, all of which will be introduced together below.

2. ISO (European/International) Keyboard System

ISO stands for International Organization for Standardization. The keyboard layout it defines is mainly popular in Europe, the UK, the Middle East, and parts of Asia. If you purchase a European-version laptop or a keyboard sold in the European market, you will likely encounter the ISO layout.

  • Core characteristics: The most distinctive feature of the ISO layout is the inverted L-shaped Enter key (spanning two rows in height, with the upper portion being 1.25u wide and the lower portion extending to 1.5u wide on the next row), and the shorter Backspace key located to the left of the Enter key (only 1u wide, appearing very compact compared to the 2u width of ANSI). The left Shift key is compressed to 1.25u width, and an additional key (usually "\ |") is added on the right side. The modifier keys on either side of the spacebar are also slightly different in arrangement. Overall, ISO squeezes one extra key into the area around the Enter key.
  • Keycap compatibility: This is the biggest pain point for ISO layout users. Due to its much lower market share compared to ANSI, many keycap sets do include ISO adaptation kits (usually labeled "ISO Enter" or "ISO Kit"), but they need to be purchased separately or selected as a specific variant. If you use an ISO keyboard and plan to replace keycaps, be sure to confirm before purchasing that the keycap set includes the ISO-specific Enter key, left Shift, and the additional R1-height key.
  • Symbols and multilingual support: The ISO layout was originally designed to make it easier for users of different languages to input their respective special characters. For example, on a UK ISO keyboard, the positions of @ and " are swapped compared to ANSI, while a German ISO keyboard adds extra keys for umlaut characters like Ä, Ö, and Ü on the right side. For users who need to work with multiple European languages, the ISO layout offers more flexible character input capabilities. But for users who primarily use Chinese and English, the ANSI layout is usually more straightforward.

The ISO system also has a complete size specification lineup from full-size to 60%, with key counts generally one more than the equivalent ANSI specification due to that extra key.

3. Keyboard Size Specifications Explained

Whether in the ANSI or ISO system, keyboards are divided into different size specifications based on how many keys are retained. The smaller the specification, the more compact the keyboard and the less desk space it occupies, but it also means more keys are integrated into combination keys (Fn layer).

  • Full-Size: 104 keys in ANSI, 105 keys in ISO. This is the most complete keyboard form, containing the main typing area, function key row (F1-F12), navigation cluster (arrow keys, Insert, Home, PgUp, etc.), and the numeric keypad. It is suitable for accountants, data analysts, and anyone who frequently needs to input numbers, or for users who are accustomed to the standard layout and don't want to make any compromises. The downside is that it takes up the most desk space, squeezes the mouse movement area, and the right-side numeric keypad is not frequently used by most non-numeric workers.
  • TKL (Tenkeyless): 87 keys in ANSI, 88 keys in ISO. It removes the numeric keypad on the far right while retaining the full function key row and navigation cluster. This is currently the sweet spot choice for many gamers and office users—it gives the right hand more room for the mouse while preserving the arrow keys and F-row, so no combination keys are needed for those operations. TKL is also one of the best sizes for keycap compatibility.
  • 75%: Approximately 84 keys in ANSI, 85 keys in ISO. It further compresses space compared to TKL by vertically integrating the navigation cluster (Insert, Home, PgUp, etc.) on the right side of the keyboard, with the arrow keys pressed closely against the main typing area. The overall arrangement is more compact. A 75% keyboard retains almost all physical keys while reducing the width to just about one key shorter than a TKL. It suits users who want compactness without sacrificing physical arrow keys and the F-row, but the navigation key positions take some time to get used to.
  • 65%: Approximately 68 keys in ANSI, 69 keys in ISO. It continues the trimming process by removing the top function key row (F1-F12), keeping only the main typing area, arrow keys, and a few of the most commonly used navigation keys (usually Del, PgUp, PgDn). F-row functions are accessed via Fn + number keys. 65% is currently a very popular entry-level compact size that strikes a great balance between portability and practicality, but users accustomed to F-row shortcuts will need to adapt to the Fn layer operation method.
  • 60%: Approximately 61 keys in ANSI, 62 keys in ISO. The keyboard is trimmed to the extreme, keeping only the core main typing area. Arrow keys, navigation keys, and the F-row are all removed, with all missing keys accessed through Fn combination keys or custom layers. A 60% keyboard is the smallest and most portable, offering an extremely clean desktop look. It is deeply loved by minimalists and users who need to frequently carry their keyboard with them. However, the learning curve is also the steepest of all specifications—you need to memorize a large number of key combinations, and efficiency may drop when you need to frequently use arrow keys or the F-row.

4. Apple Keyboard System

Although Apple keyboards are physically close to ANSI in arrangement, they have their own uniqueness in modifier key layout and system mapping, and deserve to be explained separately.

  • Standard compact layout (approximately 78 keys): Apple's Magic Keyboard and MacBook built-in keyboards use a unique layout that falls somewhere between 75% and 65%. It retains the top F-row (but the F-keys are mapped by default to system control functions such as volume and brightness), and the arrow keys use an inverted-T design, but with gaps below the left and right arrow keys. The bottom row modifier keys are arranged as Ctrl, Option (Alt), Command (Win), with different functional mappings compared to Windows keyboards—in macOS, the Command key takes on the role that the Ctrl key plays in most Windows shortcuts.
  • Keycaps and feel: Apple keyboards use an ultra-thin scissor-switch structure with extremely short key travel, which feels vastly different from mechanical keyboards. Their keycap sizes and stem specifications are proprietary to Apple and cannot be interchanged with the universal MX-style keycaps on the market. If you use a Mac but want an external mechanical keyboard, choosing one that explicitly supports Mac mode switching (swapping the Alt and Win key mappings via a switch or software) would be a more flexible option.

5. How to Choose the Right Keyboard System and Size for You

Faced with two layout systems—ANSI and ISO—and five mainstream size specifications, making a choice requires considering your actual usage scenarios and preferences.

  • Prioritize the ANSI system: Unless you live in Europe and use a local language layout, or you particularly love the feel of the inverted L-shaped Enter key, ANSI is the safer choice. It has the richest selection of keycap accessories, the lowest replacement costs, and a more active aftermarket and second-hand market.
  • Decide on size based on usage frequency: Dealing with numbers every day? A full-size keyboard or a standalone numeric keypad is better for you. Need frequent access to the F-row but want a clean desk? TKL or 75% is the ideal range. Extremely limited desk space or need to carry the keyboard around? 65% or 60% will be a delight. If you're unsure, TKL is the safest compromise—it retains almost all commonly used keys while freeing up valuable mouse movement area.
  • Additional considerations for Mac users: If you primarily use macOS, prioritize keyboards that explicitly state Mac mode switching support, so the Command and Option key positions match Apple's native keyboard and you don't need to modify mappings in system settings. Also note that Bluetooth connectivity stability is generally better on Mac than on Windows, and can be the top choice for wireless setups.
  • Try it in person before deciding: Ultimately, you need to physically try different keyboard sizes and layouts to know what feels right. If possible, visit a physical store to try typing on different sizes, or start with an affordable entry-level model in a certain specification, and only upgrade to a higher-end model once you've confirmed your preference.

The classification of keyboard systems and sizes may seem complex at first glance, but the entire knowledge framework becomes clear once you grasp the two main threads: the visual differences between ANSI and ISO, and the step-by-step simplification logic from full-size to 60%. Whether you ultimately choose a 104-key full-size ANSI or a 62-key minimalist ISO, understanding the design philosophy behind these layouts will help you better understand every trade-off you make. I hope this guide serves as your first reliable map for exploring the world of keyboards.