PhiTeX ⚡ Instant
Instant LaTeX preview for VS Code: the pages update as you type, typeset
by PhiTeX inside VS Code itself. No TeX installation is needed.
PhiTeX is a TeX engine that rebuilds incrementally. An edit re-runs only
what it changed, so ordinary text and headings reach the page in a few
milliseconds.
PhiTeX 1.0's PDF is the one pdflatex makes, byte for byte, and the
tests check that after every edit. If you ever find a difference, it's a
bug: please report it.
Getting started
Open a .tex file and press Ctrl+Alt+P (Cmd+Alt+P on a Mac), or
click the ⚡ button in the editor's title bar. The preview opens beside the
editor.
The builtin engine downloads the TeX packages a project uses, and asks
before its first download. They are kept for next time, so later builds
start in seconds. To use your own TeX Live instead and download nothing,
choose Use my TeX Live there: the preview then runs on the phitex
command (the setting phitex.engine, "phitex watch").
What it does
- Pages as you type: every edit is typeset at once, with no save and no
Recompile button.
- pdfLaTeX and XeLaTeX: fontspec, unicode-math and polyglossia, with
TeX Live's OpenType fonts or your own. A
% !TEX program = … line picks
the engine, else the preamble does (phitex.texEngine).
- Link previews: rest the pointer on a
\ref, an \eqref or a
\pageref and a small window shows that spot of the target page. Pin it,
move it, resize it from its corner.
- Citation cards: hover a citation for a card per cited work. A group or
a range like [1–3] shows every work in it, the one under the pointer
marked.
- Back and forward: follow a link and a Back pill appears, with the
places you came from; the mouse's back and forward buttons work too.
Ctrl+click (or a middle click) opens the target in a new preview tab.
- Source ↔ page: the word at your cursor is marked on the page.
Double-click the page to jump to its source; select text on the page to
select it in the editor.
- Compare with a past version: mark a From and a To in the folder's git
history. The changes are marked on the pages as
latexdiff marks them,
and the marks follow your edits. Without git it says what it needs; you
commit with your own git or Source Control.
- Problems: errors and warnings are listed in the preview and underlined
on the page where they happen. View log shows the build's log.
- Bibliographies and indexes: BibTeX, biber and makeindex run inside the
build, so references settle by themselves.
- minted: code blocks are highlighted by Pygments, which runs inside the
extension.
- Contents: the document's outline beside the pages.
- Loading animations: Settings › Appearance plays each one; pick any
number, or none (
phitex.opening).
Engines
- builtin (the default): PhiTeX compiled to WebAssembly, running in VS
Code's extension host. Nothing to install.
- phitex watch: the native
phitex command, if you have it installed
(set phitex.path).
Switch Engine in the command palette changes between them.
Settings
| Setting |
Default |
What it does |
phitex.engine |
builtin |
Which engine typesets the preview: builtin or phitex watch. |
phitex.path |
phitex |
The phitex command for the phitex watch engine: a name on the PATH or a full path. |
phitex.texEngine |
auto |
The builtin engine's TeX: auto (a % !TEX program line, else the preamble), pdflatex or xelatex. |
phitex.main |
(empty) |
The project's main .tex file, relative to its folder. Empty: the open file if it has \documentclass, else the folder's file that has it. |
phitex.follow |
cursor |
What the pages mark of where you are in the source: cursor, selection or dblclick. |
phitex.threads |
0 |
The builtin engine's threads. 0: one per core of this machine, at most 4. |
phitex.darkPdf |
off |
Dark pages: off, on, or theme (when VS Code's theme is dark). |
phitex.opening |
random |
The loading animations: random, all, off, or those picked, comma separated. |
phitex.underline |
true |
A wavy line on the pages under what each error and warning is about. |
phitex.trace |
false |
Write what the preview does to the PhiTeX output, for a bug report. |
Privacy
Your documents never leave your machine. The typesetter runs inside VS
Code, and so does Python for minted.
For a TeX package it doesn't bundle, the extension downloads that package
from Shelf (v1.shelf.phitex.org, or shelf-phitex-v1.pages.dev where
that cannot be reached), static files on Cloudflare Pages. It sends a plain
GET request for the package's file, such as …/tl2026/h/pgf-3f9a2c41b0de.pack.
At most once a day it also reads …/tl2026/release.json to learn of a newer
package index. No document text, file name of yours, or identifier is sent.
Cloudflare sees the request and your IP address, as with any website. Shelf
keeps no logs of its own.
There are no analytics, no accounts and no tracking.
Limits
- LuaLaTeX projects don't run yet; pdfLaTeX and XeLaTeX do.
- Images: PDF, PNG and JPEG figures work.
- Shell escape is restricted, as in TeX Live's
pdflatex, and only
minted's command runs.
- Some packages and fonts aren't fully supported yet, for example
microtype's font expansion. When the engine stops on something it can't
do, the problems list names it.
- Speed varies with what you edit. Editing a macro that a big TikZ
picture uses on every point can take a second or more.
- Very large TikZ documents: one the size of the TikZ manual (1,180
pages) runs out of memory in the builtin engine; use
phitex watch.
License
AGPL-3.0-only. PhiTeX is made by the Accelerated Connected Computing Lab
(ACCL) at KAUST. Source: https://github.com/accl-kaust/PhiTeX-frontends.
