Features›Scrollback›Scroll up (SU)

Scroll up (SU)

Category: scrollback · Baseline: core · Tags: ECMA-48 Standard, VT510 · Specification ↗

ESC [ N S

SU scrolls the content within the scroll region up by N lines, inserting blank lines at the bottom. The sequence is ESC [ N S (default N=1). Lines scrolled off the top enter the scrollback buffer (on the main screen). Used by applications to scroll content without moving the cursor.

How this is testedautomated
Write "TOP" on row 1 then fill the screen, send \x1b[S (SU 1), verify row 0 no longer starts with "T".

The same probe runs against headless backends (via Termless) and real terminal apps (via a daemon launched in each terminal). This lets us distinguish parser correctness from rendering correctness.

Analysis2026-04-06

Supported by all 12 tested terminals — universal adoption. Part of the Core TUI baseline.

Supported by 12 of 14 backends (86%)

Terminal Applications

Terminal	Version	Support	Notes
iTerm2	3.6.9	✓ yes
Ghostty	1.3.1	✓ yes
VS Code		✓ yes
Warp		✓ yes
Cursor		✓ yes
Terminal.app		✓ yes

Headless Backends

Parser correctness only — a ✓ means the parser accepts the sequence.

Backend	Version	Support	Notes
Alacritty	0.26.0	✓ yes
Kitty	0.40.0	✓ yes
vt100.js	0.2.1	✓ yes
vterm	0.2.0	✓ yes
WezTerm	0.1.0-fork.5	✓ yes
xterm.js	5.5.0	~ partial	Headless API reads from buffer, not viewport after scroll

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