ASCII Lookup

Introduction

The ASCII Lookup tool provides a complete ASCII code table (0-255), split into three independent tables: control characters (0-31, 127), printable characters (32-126), and extended ASCII codes (128-255). Each character's decimal (DEC), hexadecimal (HEX), octal (OCT), and binary (BIN) values are displayed alongside its HTML numeric entity and HTML named entity. Each range has its own dedicated table, rendered server-side and ready to use — no searching or filtering needed.

Whether you're debugging network protocols, studying character encoding fundamentals, writing HTML entity conversion code, or brushing up on computer science basics, this tool serves as a convenient always-available reference.

Technical Principles

ASCII (American Standard Code for Information Interchange) is a character encoding standard based on the Latin alphabet, first published in 1963 and updated in 1967 to a 7-bit standard covering both uppercase and lowercase letters. Standard ASCII uses 7 binary bits to represent 128 characters (0-127): 33 non-printable control characters (used for terminal device control and communication protocols) and 95 printable characters (digits, letters, punctuation).

Extended ASCII (128-255) uses the 8th bit to expand the character set to 256. This extended range varies across encoding standards. This tool uses the Windows-1252 standard to display extended ASCII characters, including accented letters used in European languages, currency symbols, and special characters. In HTML, any ASCII character can be represented using &#NN; (numeric entity) or &NAME; (named entity, supported for select characters only), which is particularly useful in web development.

Use Cases

• Software development and debugging: quickly look up ASCII values for specific bytes when handling string encoding, network packet parsing, or binary protocols
• HTML/XML entity encoding: find corresponding entity names and codes when converting special characters to HTML entities in web development
• Computer science education: serve as a complete ASCII encoding reference when studying computer fundamentals, digital circuits, or encoding theory
• Serial communication and embedded development: check hexadecimal and binary representations of control characters when debugging UART, SPI, and other serial protocols
• Text file format analysis: quickly locate control characters for line endings (CR/LF/CRLF) when analyzing text files from different operating systems

Frequently Asked Questions

What is the difference between ASCII and Unicode?

ASCII can only represent 128 characters (256 with extended range), mainly covering English letters, digits, and basic symbols. Unicode is a more comprehensive encoding standard that supports virtually all writing systems worldwide (including Chinese, Japanese, Arabic, etc.) and can represent over 140,000 characters. UTF-8 is an implementation of Unicode that is backward compatible with ASCII — ASCII characters occupy 1 byte in UTF-8 with the same code values.

Will extended ASCII codes display the same across different systems?

Not necessarily. Extended ASCII codes (128-255) map differently across various encoding standards. This tool uses the Windows-1252 standard, one of the most common extended ASCII mappings. However, characters in the 128-255 range may appear differently under other operating systems or code pages. For international character support, Unicode (UTF-8) is recommended.

What is the difference between HTML numeric entities and named entities?

HTML numeric entities use the &#decimal; format and are supported for all 256 ASCII characters. HTML named entities use more memorable names (such as © for ©) but are only defined for a subset of commonly used symbols. In HTML documents, both render correctly, but named entities offer better readability.

Typical Usage

Scenario: Look up all encoding representations of the letter "A".

1. Open the ASCII Lookup tool — three encoding tables are displayed automatically
2. Find the character "A" in the "Printable Characters" table (row with decimal 65)
3. The row shows all encoding values: Decimal 65, Hexadecimal 41, Octal 101, Binary 01000001, HTML numeric entity A
4. The Description column also provides the character name or explanation

Related Tools

ASCII is the foundation of character encoding. The Base Converter helps you understand conversion between different number systems. For URL special character encoding, the URL Decoder and URL Encoder are also useful. In text processing, the Text Diff tool can help identify text encoding differences.