Standard ASCII is a 7-bit character set containing exactly 128 code positions, from decimal 0 through decimal 127, and each position has the same value expressed as a two-digit hexadecimal, a three-digit octal, and a seven-digit binary number. On a Mac, these codes show up everywhere a developer, writer, or analyst works: in source files, terminal output, network traces, and clipboard payloads. The fastest way to look up any standard ASCII code on macOS is a browser-based reference such as the ASCII Table, which lists all 128 rows with their decimal, hexadecimal, octal, and seven-bit binary values, alongside the visible character or RFC 20 control abbreviation and a descriptive name. Because the table is created and filtered entirely in the browser, you can search it without installing anything on your Mac, copy a complete row to the clipboard, and confirm the exact code point you need for a code comment, a bug report, a protocol note, or a debugging session.
Why Mac Users Need a Quick ASCII Reference
ASCII is the foundation that most modern text tools on macOS still build on. The Unicode Basic Latin block, which every Mac app uses for English text, assigns the same code points to the standard ASCII characters, so when you read a byte from a file, paste a control sequence into a Terminal window, or inspect a log line, you are usually reading an ASCII value even if the file is stored in UTF-8.
You will encounter ASCII codes on macOS when:
- Writing source code that compares characters against their numeric code points
- Inspecting raw bytes from a network protocol such as HTTP, SMTP, or FTP
- Decoding a string that contains stray control characters like CR, LF, or NUL
- Replacing mojibake or non-ASCII bytes with the correct character in a downloaded file
- Verifying that a CSV or TSV file is really ASCII-safe before importing it into Numbers or a database
- Confirming that a binary blob copied to the clipboard contains only printable characters before pasting it into a chat
A complete, standards-backed reference removes guesswork. Instead of typing values from memory, you can confirm that capital A is decimal 65, hexadecimal 0x41, octal 0o101, and binary 0b1000001, and then drop the exact notation into your code or your notes without re-checking a textbook.
Mac Methods for Entering and Checking ASCII Codes
macOS ships with several built-in ways to enter or inspect ASCII characters, and each is useful in a different situation. Knowing what your operating system already offers helps you decide when a browser reference is the better tool.
| Mac method | How to open it | Best for |
|---|---|---|
| Character Viewer | Press Control-Command-Space from any app | Browsing and inserting printable characters and symbols |
| Unicode Hex Input | Add the input source via System Settings, Keyboard, Input Sources, then hold Option and type a four-digit hex code | Inserting a specific Unicode code point by hexadecimal |
| Terminal utilities | Run man ascii, xxd, or od -c on a file | Inspecting raw bytes from a stream or a file |
| Browser reference | Open the ASCII Table in Safari, Chrome, or another browser | Looking up decimal, hexadecimal, octal, and binary values for any of the 128 standard codes and copying the row |
The first three options are excellent for the narrow tasks they cover, but they do not give you a complete 128-row table that shows all four radix values at once. When you need a printable reference for a code comment, a teaching slide, a bug report, or a quick cross-check against a network trace, the browser-based ASCII Table fills that gap without leaving your Mac.
Looking Up Any ASCII Code with the ASCII Table Tool
The ASCII Table on Lizely is designed to be opened in any tab on macOS and used without an account, a download, or a network round trip after the page loads. It is a focused reference for the standard 7-bit American Standard Code for Information Interchange, lists exactly 128 code positions beginning with decimal 0 and ending with decimal 127, and shows the same code in decimal, two-digit hexadecimal, three-digit octal, and seven-digit binary alongside a visible character or control abbreviation, a descriptive name, and a practical category.
To look up a code on your Mac:
- Open the ASCII Table in your browser and let it load all 128 rows.
- Type a character name, an RFC 20 control abbreviation, a decimal value, a prefixed radix value, or a char:value term such as char:0 or char:space into the search box.
- Choose a category from the filter when you want to isolate controls, punctuation, digits, letters, Space, or Delete.
- Read the row, then select Copy to write one complete row to your clipboard in a readable text format that includes the display value, the name, and all four number systems.
Search and category changes update the table immediately. If nothing matches your query, the page shows a clear no-match state instead of leaving stale rows on screen. If your browser denies clipboard access, the page reports the failure rather than pretending the copy worked, so you can grant the permission and try again without losing your place.
Searching by Decimal, Hex, Octal, and Binary
One of the most common reasons Mac users open an ASCII reference is that documentation, source code, network traces, and command-line tools all use different notations for the same number. The ASCII Table accepts each of them and resolves every form to the same row.
| Search term | Interpreted as | Example for capital A |
|---|---|---|
| Plain digits | Decimal value | 65 |
| 0x prefix | Hexadecimal value | 0x41 |
| 0o prefix | Octal value | 0o101 |
| 0b prefix | Binary value, seven digits | 0b1000001 |
| char:value | One explicit literal character | char:A or char:space |
| Plain words | Descriptive name or phrase | line feed, question mark |
If you paste 0x41 from a hex dump, type 65 from a C-style character literal, or copy 0o101 from a Unix permission listing, the table shows you capital A with every notation side by side, which is much faster than converting each value by hand on a calculator. Phrases also work: searching for line feed, question mark, capital letter, or tab brings up the matching row, with the RFC 20 abbreviation shown next to the full name. This is useful when you remember what a code does but not the number itself.
Copying a Complete Row for Notes and Code
When you have found the row you need, the Copy button writes one complete entry to the clipboard in a readable text format. The copied row includes the display value, the descriptive name, and the code in all four number systems, which makes it drop-in ready for code comments, commit messages, debugging notes, and protocol documentation.
Typical uses for the copied row on macOS include:
- Writing a comment in a C, C++, Swift, or Rust file that explains what a numeric literal represents
- Adding the exact code to a bug report so a teammate does not have to look it up again
- Pasting the notation into a teaching slide, a wiki page, or a chat message
- Adding the value to a data-cleaning rule that strips or replaces a specific control character
- Including the row in a comparison table when you are documenting the difference between two encoders or protocols
Copying happens entirely in your browser. Search terms and copied rows are not sent to Lizely or to another service, which means the reference is safe to use even when you are working with sensitive byte values from a local capture file. Clipboard access depends on your browser permission, and the page surfaces a real error if the copy is denied so you can grant access and try again. Changing the search term or category clears an earlier copy message, so the on-screen state always reflects your current selection.
Why Standard ASCII Stops at Decimal 127
The 7-bit boundary is deliberate, and it matters on a Mac because the operating system happily decodes byte values above 127 in many different encodings. Standard ASCII contains only decimal 0 through 127, so the reference stops at decimal 127 and does not include decimal 128 through 255.
Those higher byte values may represent different characters in ISO-8859-1, in Windows code pages, and in IBM PC code pages such as CP437. Calling all of them "extended ASCII" hides a real ambiguity: a single byte above 127 can decode to a different character depending on the encoding that produced it. The ASCII Table intentionally does not combine these incompatible 8-bit mappings, so every row it shows is unambiguous. If you are debugging a byte above 127 on your Mac, first identify the actual character encoding that produced it. Choosing an encoding is part of decoding; the number alone is not enough. Once you know whether the byte came from ISO-8859-1, CP437, UTF-8, or another encoding, you can interpret it correctly.
Standard ASCII also assigns codes to non-printing positions, and the table makes that visible. Control positions from decimal 0 through 31 use the abbreviations and terminology published in RFC 20. Examples include NUL for Null, HT for Horizontal Tabulation, LF for Line Feed, and CR for Carriage Return. Decimal 32 is shown explicitly as SP for Space, and decimal 127 is shown as DEL for Delete and placed in its own Delete category because RFC 20 notes that DEL is not a control character in the strict sense. This distinction keeps the visible categories honest instead of treating every non-printing position as identical.
For graphic entries from decimal 33 through 126, the table follows the Unicode Basic Latin code chart for names while keeping the code positions aligned with the RFC 20 ASCII table, so a single lookup on your Mac gives you values that are correct in both standards. The 7-bit scope is independently confirmed by ECMA-6, which defines exactly the same 128-character set. Together these references mean you can trust every row in the table to match what your Mac, your Terminal, your text editor, and your network analyzer actually call the same code.