I try to improve the time pdflatex needs to compile my book.

Really working example






I run the following commands on bash console:

$ pdflatex -ini -jobname="preamble" "&pdflatex preamble.tex\dump"
$ latexmk -pdf -pvc -e '$latex=q/latex %O -shell-escape %S/' book.tex

A window opens with a (nearly) live preview that will be updated after each change in the book.tex file. The PDF Viewer evince reloads automatic when the .pdf changed.

Open Questions

I had no success to compile with the preamble of my book in the preamble.tex file.

  • How can I find out what I can precompile?
  • Can I precompile \newcommand's, \usepackage's?
  • Can I precompile a pure chapter without header?

Other aproaches for speed up

(I do not understand how to combine this ideas for best result)

  • pdflatex knows a -draftmode I measured 20% faster compilation with time pdflatex -draftmode 50pagetest.tex
  • 3
    If you \include many chapters you can use \includeonly in your master file (book.tex) to compile just the chapters you are editing at the moment. Oct 29, 2012 at 0:56
  • 2
    @Jonas Yes \include and \includeonly works only with separating the file's content on different pages. But for your final compilation you can change those \includeonly back to \inputs. • Also related: mylatexformat Oct 29, 2012 at 1:22
  • 1
    @JonasStein You can create a format (precompile) preloading packages, and \newcommand. With mylatexformat you can compile files with the same preamble, the files must have a \begin{document} and \end{document}
    – Guido
    Oct 29, 2012 at 3:11
  • 2
  • 1
    @JonasStein: Could you post a MnWE for your (failed) separation of your book document into preamble.tex and book.tex? Also, what is the exact wording of the error message?
    – krlmlr
    Oct 29, 2012 at 19:51

2 Answers 2


"precompile" is probably a slightly confusing phrase to use as TeX is not a compiler but (mostly) a macro expansion language, but anyway...

In general you can dump most macro definitions and register assignments into a format. What you can't do is ship out pages. So in practice you can dump most LaTeX preambles.

Rather than having to edit the file so that it only works with the preloaded preamble format it is possible to leave the preamble as normal, but define the dumped format to skip the commands that were previously executed in the dump.

My truly ancient mylatex files on ctan do this or there is a newer version of that with additional features and better maintained: mylatexformat

The main thing you have to beware of (and which I suspect you are falling over) is if any of commands that you dump use \jobname (for example to open auxiliary files) then you have to ensure that the jobname when you dump the format is the same as the jobname when you produce the document. Also If the macros are assuming that files opened by commands in the preamble are still open when the document is processed then you will need to re-open them when you use your preloaded format loading the format file will re-set TeX's internal state with respect to its internal memory but it will not re-assign the file handles to the filesystem.

The first hit on searching for mylatex on this site shows an example discussing this in the context of tikz externalize.

TikZ's externalization and mylatex

I wrote the above back in 2012, If writing it now I would stress two other classes of things that can not be dumped.

  • OpenType fonts (so affecting any xelatex or lualatex preamble that loads system fonts), and
  • Lua state, so affecting any package that uses \directlua if used with luatex. For any particular Lua code you can usually \dump a macro definition that executes the code in \everyjob or \AtBeginDocument however this often requires substantial re-arrangement of the package code, so using mylatex with an unchanged latex document is often not possible when using lualatex.
  • I definitely like leaving the preamble intact and skipping it when not needed, such as when submitting tex files to a publisher. However, this means that when I checkout the document from a git repo (which does not hold the fmt file, obviously) the document will compile fine, without any warning that a precompiled format has not been used. Is there a way for me to issue a warning if the fmt file has not been found? I could maybe check for the existence of the fmt file, but is there a more "internal" approach to this?
    – bers
    Oct 6, 2020 at 9:01
  • @bers \IFFileExists{\jobname.fmt}{....}{...} ? Oct 6, 2020 at 10:19
  • yes, this is what I ended up doing. I had been looking for something that ensures not only that the file exists, but that it has been used, too. I have now added \ifcsname endofdump\endcsname\else\PackageWarning{mylatexformat}{Precompiled header not used}\fi.
    – bers
    Oct 6, 2020 at 14:55

For the benefit of people using a search engine arriving here looking for how to convert a never-changing but slow-loading preamble into a super-quick "precompiled" format.

The instructions here take you through a simple process, as follows. You need the mylatexformat package to make this work.

  1. Split your preamble into "static" and "might change" stuff, with the static stuff first.

  2. At the end of the static stuff add the command \endofdump

  3. Run the following from the command line/terminal, replacing both instances of foo with the name of your document:

    pdftex -ini -jobname="foo" "&pdflatex" mylatexformat.ltx foo.tex
  4. Insert the code %&foo at the top of your .tex file, replacing foo with the name of your file.

Your compiles will now happen much faster.

Note: if you have any "might change" preamble, you need to keep the \endofdump command, otherwise compilation will start at \begin{document} skipping all your preamble.

  • 2
    Step 4 (deleting the precompiled preamble) is not needed. The generated format loads mylatexformat which skips content until \endofdump. Viceversa, if you're ready to delete content, you needn't mylatexformat, you just need to use the \dump command as explained here: web.archive.org/web/20170718172440/http://… Jul 18, 2017 at 17:26
  • @Blaisorblade wow, this really makes the workflow much, MUCH simpler. Love it.
    – LondonRob
    Jul 18, 2017 at 19:18
  • Thanks! Meanwhile, I've taken tex.stackexchange.com/a/37730/1340, dropped mylatexformat, adapted it a bit (sorry, not published yet) and now get the prelude auto-recompiled by latexmk on changes (though it need be a separate file for that), which seems even better (YMMV)! Jul 18, 2017 at 20:57
  • 1
    To save time for future visitors, note that this doesn't work with XeLaTeX and LuaLaTeX: tex.stackexchange.com/questions/49295/… (loaded OTF fonts can't be dumped, and most big packages load OTF fonts)
    – Clément
    Dec 15, 2021 at 1:11
  • Addition: ■ If your preamble is the whole part before \begin{document} then you can skip the \endofdump step. ■ If there's some part in the preamble that cannot be precompiled (e.g. unicode-math in LuaLaTeX, as mentioned in the comment above), you should put it after \endofdump i.e. in the "dynamic" part.
    – user202729
    Jan 18 at 15:37

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .