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ECMA-48 Standard
Features defined in the ECMA-48 standard (also known as ISO/IEC 6429 and ANSI X3.64). ECMA-48 defines the CSI (Control Sequence Introducer) grammar that all modern escape sequences use, including SGR (Select Graphic Rendition) for text styling, cursor movement (CUP, CUU, CUD, CUF, CUB), erase operations (EL, ED), and scroll control (SU, SD). First published in 1976 (5th edition 1991), the standard itself is frozen — but terminals continue to extend the SGR parameter space with vendor extensions (e.g., Kitty's underline variants SGR 4:3–4:5) that use ECMA-48's sub-parameter syntax without being part of the standard. The 1976 first edition defined just the basics; by the 5th edition in 1991, it had grown to cover 8-bit controls, mode switching, and the sub-parameter syntax that modern extensions rely on. ECMA has not revised it since — making it one of the longest-frozen standards still in active daily use.
ECMA-48's core contribution is the CSI grammar: ESC [ followed by numeric parameters separated by ;, terminated by a letter that identifies the function. For example, ESC [1;31m activates bold red text (SGR 1 = bold, SGR 31 = red foreground). This grammar is extensible by design — parameters can include sub-parameters separated by :, which is how modern extensions like Kitty's underline styles (SGR 4:3 for curly underline) fit within the standard's syntax without violating it.
The standard defines three fundamental feature groups that every terminal must support: cursor control (CUP for absolute positioning, CUU/CUD/CUF/CUB for relative movement), erase operations (ED to clear regions of the screen, EL to clear parts of a line), and text styling via SGR (bold, italic, underline, blink, inverse, strikethrough, and 8/16 named colors). SGR 0 resets all attributes — a sequence every CLI tool emits to avoid style leakage.
For developers, ECMA-48 compliance is the absolute minimum bar. If a terminal doesn't handle basic CSI sequences correctly, nothing works — not shells, not editors, not TUI frameworks. The standard is freely available as a PDF from ECMA International, and at 113 pages it remains one of the most concise foundational specs in computing.
Analysis2026-04-06
Terminal Applications
Headless Backends
Parser correctness tested via Termless. A ✓ means the parser accepts the sequence, not that it renders correctly.