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Enter ASCII text or characters Type any ASCII characters (0–127). Non-ASCII characters will be flagged.

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Char	ASCII Dec	ASCII Hex	PS/2 Set 1	PS/2 Set 2	USB HID	Modifier	Key Name

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About

Keyboard scan codes are the raw hardware-level identifiers sent by a keyboard controller to the host system. They differ fundamentally from ASCII values. A PS/2 keyboard using Set 1 (XT) sends 0x1E for the A key, while Set 2 (AT) sends 0x1C for the same physical key. USB HID keyboards use an entirely separate Usage ID table defined in the USB HID Usage Tables specification (Document v1.4). Confusing these code spaces is the most common source of bugs in firmware development, OS kernel input drivers, and bootloader keyboard handlers. This tool maps all 128 standard ASCII code points (0 - 127) to their corresponding PS/2 Set 1 Make code, PS/2 Set 2 Make code, and USB HID Usage ID. Extended codes (E0-prefixed) for keys like arrows or Insert are included where applicable.

Limitations: this mapping assumes a US QWERTY layout. Shifted characters (e.g., ! at 0x21) map to the base key’s scan code plus a Shift modifier flag. Non-printable control characters (0x00 - 0x1F) are mapped to their conventional key equivalents where a direct physical key exists (e.g., Tab, Enter, Escape, Backspace). Characters with no standard single-key mapping are marked accordingly.

Formulas

The conversion is a direct lookup operation. No arithmetic formula is involved. Each ASCII code point c is used as an index into a mapping table T that returns a tuple of scan codes:

T(c) → (S₁, S₂, U, m)

Where S₁ = PS/2 Set 1 Make code, S₂ = PS/2 Set 2 Make code, U = USB HID Usage ID, and m = modifier flag (Shift required: TRUE or FALSE). For uppercase letters and shifted symbols, the base key scan code is returned with m = TRUE, indicating the host must also send/register the Shift modifier (PS/2 Set 1: 0x2A, USB HID: 0xE1). The valid domain is c ∈ [0, 127] ⊂ Z. Values outside this range produce no mapping.

Reference Data

ASCII	Dec	Hex	Char	PS/2 Set 1 (Make)	PS/2 Set 2 (Make)	USB HID	Key Name
0	0	0x00	NUL	-	-	0x00	No Event
8	8	0x08	BS	0x0E	0x66	0x2A	Backspace
9	9	0x09	TAB	0x0F	0x0D	0x2B	Tab
13	13	0x0D	CR	0x1C	0x5A	0x28	Enter
27	27	0x1B	ESC	0x01	0x76	0x29	Escape
32	32	0x20	SP	0x39	0x29	0x2C	Space
48	48	0x30	0	0x0B	0x45	0x27	0 Key
49	49	0x31	1	0x02	0x16	0x1E	1 Key
50	50	0x32	2	0x03	0x1E	0x1F	2 Key
57	57	0x39	9	0x0A	0x46	0x26	9 Key
65	65	0x41	A	0x1E	0x1C	0x04	A Key
66	66	0x42	B	0x30	0x32	0x05	B Key
67	67	0x43	C	0x2E	0x21	0x06	C Key
87	87	0x57	W	0x11	0x1D	0x1A	W Key
88	88	0x58	X	0x2D	0x22	0x1B	X Key
89	89	0x59	Y	0x15	0x35	0x1C	Y Key
90	90	0x5A	Z	0x2C	0x1A	0x1D	Z Key
97	97	0x61	a	0x1E	0x1C	0x04	A Key
122	122	0x7A	z	0x2C	0x1A	0x1D	Z Key
127	127	0x7F	DEL	E0 53	E0 71	0x4C	Delete

Frequently Asked Questions

PS/2 Set 1 (also called the XT set) was used by the original IBM PC XT keyboard. Set 2 (the AT set) is the default for PS/2 keyboards and is what most modern PS/2-compatible controllers actually transmit. The keyboard sends Set 2 codes on the wire, but the i8042 keyboard controller in the PC translates them to Set 1 before passing them to the CPU. This is why both sets are relevant: firmware working below the i8042 sees Set 2, while BIOS interrupt handlers and legacy OS drivers see Set 1.

Scan codes represent physical keys, not characters. The A key has PS/2 Set 1 Make code 0x1E regardless of case. The distinction between uppercase A (ASCII 65) and lowercase a (ASCII 97) is produced by combining the base key scan code with the Left Shift modifier (Set 1: 0x2A, USB HID: 0xE1). This tool flags such characters with a Shift indicator.

USB HID keyboards send a structured 8-byte report containing modifier flags and up to 6 simultaneous key Usage IDs. The Usage IDs are defined in the USB HID Usage Tables document (Keyboard/Keypad Page 0x07). They start at 0x04 for A and are sequential through Z. Unlike PS/2 scan codes, USB HID codes are layout-independent identifiers assigned by the USB-IF standard body, not by the keyboard hardware vendor.

Most ASCII control characters below 32 do not correspond to a dedicated physical key. Exceptions include Tab (0x09), Enter/CR (0x0D), Backspace (0x08), and Escape (0x1B). For the remaining control codes (e.g., SOH at 0x01, STX at 0x02), they are conventionally generated by holding Ctrl plus a letter key. This tool maps those to the corresponding letter key's scan code with a Ctrl modifier note.

Yes. Keys like Delete (ASCII 127) use extended PS/2 scan codes prefixed with 0xE0. For Set 1, Delete is E0 53; for Set 2, it is E0 71. The E0 prefix signals the keyboard controller that a two-byte scan code follows. This tool displays the full multi-byte code where applicable.

This tool assumes a US QWERTY layout (ANSI 104-key). On a German QWERTZ keyboard, pressing the physical key in the Z position still sends the same scan code (0x2C in Set 1), but the OS interprets it as Y. Scan codes are layout-agnostic at the hardware level. The mapping from scan code to character is performed by the OS keyboard driver using the active keymap.