Why Is My LaTeX So Slow? 10 Ways to Speed Up Compilation

The Speed Problem

You make one small change. You hit compile. You wait... and wait... and wait.

Every second of compilation time is a break in your flow. Over a writing session, those seconds add up to hours of lost productivity.

Let's fix that.

Understanding Compilation Speed

What Happens When You Compile

Your .tex file
     ↓
[First pass: Build document structure]
     ↓
[BibTeX/Biber: Process citations]
     ↓
[Second pass: Insert references]
     ↓
[Third pass: Finalize page numbers, ToC]
     ↓
[Font subsetting and embedding]
     ↓
[Image processing and embedding]
     ↓
Your .pdf file

Each step takes time. Speed up any step, and the total time drops.

Baseline Expectations

| Document Type | Expected Time | Warning Sign | |---------------|---------------|--------------| | Simple article (10 pages) | 2-5 seconds | >15 seconds | | Research paper (20 pages, figures) | 5-15 seconds | >30 seconds | | Thesis (100 pages) | 20-60 seconds | >2 minutes | | Book (300+ pages) | 1-3 minutes | >5 minutes |

If you're exceeding these, there's room to improve.

Quick Wins (5 minutes to implement)

1. Use Draft Mode

The fastest image is the one you don't process:

\documentclass[draft]{article}
% All images become placeholder boxes

Or selectively:

\usepackage[draft]{graphicx}

Speedup: Often 50-80% for image-heavy documents

When to use: While writing/editing. Switch to final for submission.

2. Compile Selectively

Don't compile what you're not working on:

% main.tex
\includeonly{chapters/current-chapter}
 
\begin{document}
\include{chapters/intro}
\include{chapters/current-chapter}  % Only this compiles
\include{chapters/conclusion}
\end{document}

Speedup: Proportional to excluded content (50-90%)

3. Use a Faster Engine

If you're using PDFLaTeX and don't need its specific features:

# Try LuaLaTeX (often faster for font-heavy docs)
lualatex main.tex
 
# Or XeLaTeX
xelatex main.tex

Speedup: 10-40% depending on document

4. Enable Compiler Caching

Use latexmk with caching:

latexmk -pdf main.tex
# Only recompiles what changed

Create .latexmkrc:

$pdf_mode = 1;
$pdflatex = 'pdflatex -interaction=nonstopmode -file-line-error';

Speedup: 30-70% on subsequent compiles

5. Reduce Output Verbosity

Less logging = slightly faster:

\usepackage{silence}
\WarningFilter{latex}{...}

Or in compiler:

pdflatex -interaction=batchmode main.tex

Speedup: 5-10% (minor but free)

Medium Effort (30 minutes to implement)

6. Optimize Images

The #1 cause of slow compilation is oversized images.

Before importing any image:

# Check image size
identify input.png
# If larger than needed, resize
 
# For photos (JPEG compression)
convert input.png -resize 1200x -quality 85 output.jpg
 
# For diagrams (keep as vector)
convert input.png output.pdf

Optimal sizes:

• Print: 300 DPI at final size
• Screen: 150 DPI at final size
• Never more than 2x final display size

Speedup: 50-90% for image-heavy documents

7. Externalize TikZ

TikZ diagrams regenerate every compile. Externalize them:

\usepackage{tikz}
\usetikzlibrary{external}
\tikzexternalize[prefix=tikzcache/]
 
% Each diagram compiles once, then cached
\begin{tikzpicture}
  % Complex diagram here
\end{tikzpicture}

Speedup: 80-95% for TikZ-heavy documents

8. Optimize Bibliography

Large .bib files slow things down:

% Instead of your entire reference library
\addbibresource{all-references.bib}  % 500 entries
 
% Use project-specific file
\addbibresource{project-refs.bib}     % 50 entries

Extract only cited references:

biber --output_format=bibtex main.bcf -O minimal.bib

Speedup: 20-40% for large bibliographies

9. Reduce Package Loading

Every package has overhead:

% Audit your packages - do you need all of these?
\usepackage{package1}
\usepackage{package2}  % Maybe not needed?
\usepackage{package3}

Common slow packages:

• tikz (load only needed libraries)
• minted (code highlighting, consider listings instead)
• fontspec with many fonts
• microtype (worth it for final, skip for drafts)

% Load only what you need from tikz
\usepackage{tikz}
\usetikzlibrary{arrows,positioning}  % Not all libraries

Speedup: 10-30% by removing unused packages

10. Parallelize When Possible

Modern LaTeX can parallelize some operations:

# With latexmk
latexmk -pdf -pdflatex="pdflatex %O %S" -auxdir=aux main.tex

For multi-file documents, compile chapters in parallel then combine:

# Compile chapters separately
pdflatex chapter1.tex &
pdflatex chapter2.tex &
wait
# Combine with pdfpages

Speedup: 30-50% on multi-core systems

Advanced Optimizations

Use LuaTeX Instead of PDFTeX

For complex documents, LuaLaTeX is often faster:

% Document works with both, but may be faster with LuaLaTeX
\documentclass{article}
\usepackage{fontspec}  % LuaLaTeX/XeLaTeX only
\setmainfont{TeX Gyre Termes}

Precompile Preamble

For stable preambles, use format files:

# Create format (once)
pdflatex -ini -jobname=myformat "&pdflatex myformat.tex\dump"
 
# Use format (every compile)
pdflatex "&myformat main.tex"

Speedup: 20-40% by skipping preamble processing

Incremental Compilation

Some tools support true incremental builds:

# Only recompile changed pages (experimental)
latexmk -pvc -pdf main.tex

Hardware Acceleration

Where you compile matters:

| Storage | Relative Speed | |---------|---------------| | HDD | 1x (baseline) | | SATA SSD | 3-5x faster | | NVMe SSD | 5-10x faster | | RAM disk | 10-20x faster |

For very large documents:

# Create RAM disk (Linux)
sudo mount -t tmpfs -o size=512M tmpfs /tmp/latex
# Compile there
cp -r project /tmp/latex
cd /tmp/latex && latexmk -pdf main.tex

Workflow Optimization

The Two-Compile Strategy

1. During writing: Draft mode, selective compilation, fast
2. For review: Full compile, all images, complete

% In preamble:
\newif\ifdraft
\drafttrue  % Toggle this
%\draftfalse
 
\ifdraft
  \usepackage[draft]{graphicx}
  \usepackage[draft]{hyperref}
\fi

Smart Compile Triggers

Don't compile on every keystroke:

Good: Compile on save Better: Compile on save with debounce (wait 2 seconds of no changes) Best: Compile on explicit command

Separate Long Tasks

Bibliography and index processing can be separated:

# Normal edit cycle (fast)
pdflatex main.tex
 
# Only when references change (slow)
biber main
pdflatex main.tex
pdflatex main.tex

Measuring Improvement

Profile Your Compilation

Add timing to your build:

time pdflatex main.tex
# real    0m12.345s

Or detailed profiling:

pdflatex -recorder main.tex
# Check main.fls for files accessed

Track Progress

| Optimization | Before | After | Improvement | |--------------|--------|-------|-------------| | Baseline | 45s | 45s | - | | Draft mode | 45s | 12s | 73% | | Image optimization | 45s | 28s | 38% | | TikZ externalization | 45s | 15s | 67% | | Combined | 45s | 8s | 82% |

Document your improvements to know what helps most.

When to Give Up on Optimization

Sometimes the document is just large. At that point:

1. Accept the compile time for final builds
2. Use selective compilation for drafts
3. Consider tools without limits (local/Thetapad)
4. Batch your compiles (review, then compile, repeat)

A 2-minute compile for a 300-page book with 100 figures is reasonable. Fight for seconds in daily writing, accept minutes for final builds.

Summary: The Speed Checklist

Quick (do now):

• [ ] Enable draft mode for images
• [ ] Use \includeonly for active chapters
• [ ] Use latexmk for smart caching

Medium (this week):

• [ ] Optimize all images (resize, compress)
• [ ] Externalize TikZ diagrams
• [ ] Audit packages, remove unused

Advanced (if needed):

• [ ] Precompile preamble
• [ ] Move to SSD/NVMe storage
• [ ] Profile and target specific bottlenecks

Conclusion

Slow LaTeX compilation has specific causes with specific fixes:

1. Images: Optimize before importing
2. TikZ: Externalize for caching
3. Bibliography: Keep project-specific
4. Packages: Load only what you need
5. Workflow: Compile smart, not often

Implement these optimizations, and compilation becomes a non-issue. Your focus stays on writing, not waiting.

For compilation without any time limits, try Thetapad's local-first architecture.