What is the ASCII file format?
The .ascii extension identifies a plain-text file encoded entirely in the 7-bit ASCII character set (American Standard Code for Information Interchange), formalized as ANSI X3.4-1986 and ISO/IEC 646. Every byte falls in the range 0x00-0x7F: printable characters occupy 0x20-0x7E, while control codes such as tab (0x09), line feed (0x0A), and carriage return (0x0D) handle whitespace and line breaks.
The extension itself is uncommon in everyday use. Most plain-text content travels under the far more familiar .txt extension; files labelled .ascii are typically exports, data dumps, or documentation packages created by tools that want to make the encoding explicit.
Because ASCII is a 7-bit scheme covering only 128 code points, it cannot represent accented letters, non-Latin scripts, or symbols beyond the basic English alphabet. UTF-8 was designed as a superset: any file that stays within the 128-character ASCII range is byte-for-byte identical whether you call it ASCII or UTF-8, so modern software reads .ascii files transparently.
.ascii files carry no file signature (magic bytes) and no byte-order mark (BOM). Identification relies on content inspection - every byte must be below 0x80. Line endings follow the host-OS convention: LF on Unix and macOS, CR+LF on Windows. The standard MIME type is text/plain, optionally qualified as text/plain; charset=us-ascii.
Any plain-text editor opens .ascii files without conversion or plugins. Related extensions serving similar roles include .asc, .log, and .ansi.
Security & safety
RISK: LOWPlain ASCII text is among the safest file types - it contains no code and cannot execute. Open any .ascii file without concern. The only practical pitfalls are non-malicious: encoding mismatches that show garbled characters (the file isn't really 7-bit ASCII but an 8-bit/UTF-8 superset), and the rare case where a text file's extension was changed to hide a non-text payload - so if a supposed text file is unexpectedly large or binary, inspect it.
Format details
in a nutshell- 3ds Max ASCII Scene Export (.ase / 'ASCII' export) - Autodesk 3ds Max can export geometry as ASCII text (ASE); occasionally surfaces under an 'ascii' label, but the standard extension is .ase.
- ASCII art / image-to-text output - Tools like jp2a render images as ASCII-character art saved as text; it's a plain-text file of characters, not an image format.
Programs that open ASCII files
Windows3 apps
Windows Notepad
Built-in Double-click or open from Notepad; for a different encoding use File > Open and pick the encoding (or rename to .txt first). 
Notepad
Open-source Open the file; use the Encoding menu to switch (UTF-8/ANSI) if characters look garbled. 
Visual Studio Code
Free Open the file; the status bar lets you reopen with a chosen encoding if needed. 
macOS2 apps
TextEdit
Built-in Open the file (use Format > Make Plain Text). If garbled, reopen choosing the right encoding. 
Linux2 apps
gedit / GNOME Text Editor
Open-source Open the file directly; gedit auto-detects common encodings and lets you choose one. Technical details
deep spec| Encoding scheme | 7-bit US-ASCII; each character stored in the lower 7 bits of one byte (values 0-127) |
| Character set size | 128 code points: 95 printable characters (0x20-0x7E) and 33 control codes (0x00-0x1F plus 0x7F) |
| MIME type | text/plain; formally qualified as text/plain; charset=us-ascii |
| File signature (magic bytes) | None - no fixed header; identified by content inspection (all bytes below 0x80) |
| Byte-order mark (BOM) | Not used; ASCII is a single-byte encoding with no multi-byte sequences |
| Common control codes | Tab 0x09, line feed 0x0A, carriage return 0x0D; NUL 0x00 rarely appears in plain-text files |
| Line-ending convention | LF (0x0A) on Unix/macOS; CR+LF (0x0D 0x0A) on Windows; bare CR on legacy Mac OS |
| File structure | Flat byte stream with no header, no metadata block, no length prefix, and no framing |
| Native compression | None built-in; ASCII text compresses very efficiently - gzip typically achieves 3:1 or better on English prose |
| UTF-8 compatibility | Every valid ASCII file is byte-for-byte valid UTF-8; the reverse is not true when bytes >= 0x80 appear |
| Maximum valid byte value | 0x7F (DEL character); any byte >= 0x80 indicates an 8-bit extension or multi-byte encoding, not pure ASCII |
| Identification method | Content scan: all bytes must be in range 0x00-0x7F and the data must be human-readable text |
| Supported platforms | Universal - Windows, macOS, Linux, Unix, DOS, embedded and legacy systems; no OS-specific dependencies |
| Typical use cases | Source-code exports, log files, documentation packages, and data interchange requiring only basic Latin characters |
| Released | 1963 (ASCII standard); .ascii as an explicit extension is a later convention |
| Latest version | ASCII (ANSI X3.4-1986 / ISO/IEC 646) - stable; superset is UTF-8 |
| Open standard | Yes · royalty-free |
| Specification | www.rfc-editor.org |
ASCII conversions
Community Q&A
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