Here are a bunch of free online books. I update this page with new books occasionally.
computer science
- Software Engineering at Google by Titus Winters, Tom Manshreck, and Hyrum Wright
- A Data-Centric Introduction to Computing by Fisler, Krishnamurthi, Lerner, and Politz
- Programming Languages: Application and Interpretation by Shriram Krishnamurthi
- How to Design Programs by Felleisen, Findler, Flatt, Krishnamurthi
- The Nature of Code by Daniel Shiffman
- Everything curl by Daniel Stenberg et al.
- Linux Command Line Books by William Shotts (The Linux Command Line and Adventures with the Linux Command Line)
- Beej’s Guides to network programming, Unix interprocess communication, and more
- Snaptoken’s project guides
- Essential Programming Books by Krzysztof Kowalczyk, the creator of SumatraPDF
- Game Programming Patterns by Robert Nystrom
- Game AI Pro by Steve Rabin et al.
- Computer Graphics from Scratch by Gabriel Gambetta
- Complete Guide to Test Automation by Arnon Axelrod
- Handbook of Graph Drawing and Visualization by Roberto Tamassia et al.
- Teach Yourself Computer Science (collection of books)
- Green Tea Press (collection of books)
- Free Ebook Foundation’s programming books (collection of books)
- MIT Press’ open access computer books (collection of books)
- FreeComputerBooks.com (collection of books)
- Flavio Copes’ frontend web development books (collection of books)
- Dana C. Ernst’s list of free math and programming books (collection of books)
- HN discussion listing free computer science books (collection of books)
- Reddit’s list of free computer science books (collection of books)
algorithms
- Competitive Programmer’s Handbook by Antti Laaksonen
- Algorithms for Competitive Programming by adamant-pwn, jakobkogler, and RodionGork
- Algorithms (4th edition) by Robert Sedgewick and Kevin Wayne
- Crafting Interpreters by Robert Nystrom
- Algorithms for Decision Making by Mykel J. Kochenderfer, Tim A. Wheeler, and Kyle H. Wray
- Algorithms for Optimization by Kochenderfer and Wheeler
- Algorithm Design by Jon Kleinberg and Eva Tardos
- Algorithms for Modern Hardware by Sergey Slotin
- Information Theory, Inference, and Learning Algorithms by David J.C. MacKay
- Algorithms and Data Structures – Transition systems by Mikkel Nygaard and Erik Meineche Schmidt
- Algorithms by Jeff Erickson
- OpenDSA (collection of books)
Related: Algorithms
C/C++
- Essential C by Nick Parlante
- Operating Systems: Three Easy Pieces by Remzi and Andrea Arpaci-Dusseau
- Dive into Systems by Matthews, Newhall, and Webb, which also covers assembly
- Build Your Own Redis with C/C++ by James Smith
- Learn Modern C++ by Richard Spencer
Related: Learning C or C++
Python
- Automate the Boring Stuff with Python by Al Sweigart
- Python for Data Analysis (3rd edition) by Wes McKinney
- From Python to Numpy by Nicolas P. Rougier
- Scientific Visualization: Python + Matplotlib by Nicolas P. Rougier
- Python Programming And Numerical Methods: A Guide For Engineers And Scientists by Kong, Siauw, and Bayen
- Full Stack Python
- Python Data Science Handbook by Jake VanderPlas
- Pamoroso’s free Python books list (collection of books)
- Python kitchen’s Legally Free Python Books List (collection of books)
Related: Learning Python
JavaScript
Go
Related: Learning Go
Clojure
math
- Immersive Math by J. Ström, K. Åström, and T. Akenine-Möller
- Probability, Statistics, and Data – A Fresh Approach Using R by Darrin Speegle and Bryan Clair
- generatingfunctionology by Herbert S. Wilf
- BOOK OF PROOF by Richard Hammack
- Mathematics for Computer Science by Eric Lehman et al.
- Discrete Mathematics: An Open Introduction, 3rd edition by Oscar Levin
- Measure, Integration, & Real Analysis by Sheldon Axler
- Infinite Descent: An introductory pure mathematics textbook by Clive Newstead
- Dana C. Ernst’s list of free math and programming books (collection of books)
- Free Ebook Foundation’s books on math and on math for programmers (collection of books)
- American Institute of Mathematics’ books search or list (collection of books)
- OpenIntro (collection of books)
- AMS’s Open Math Notes (collection of books)
- HN discussion listing free math books (collection of books)
- Reddit’s list of free math books (collection of books)
other
- An Introduction to Geology by Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, and Cam Mosher
- The Information Literacy User’s Guide by Hosier et al.
- Lessons In Electric Circuits by Tony R. Kuphaldt
general collections
- Bookshare, for those with reading barriers
- archive.org and an alternate way to search this with typesense
- Springer’s open access books (if that link doesn’t work try this one)
- Milne Open Textbooks
- UPenn’s online books page
- Openstax
- Open Textbook Library
- Standard Ebooks
- Free Ebook Foundation’s science books
- Project Gutenberg, or bookdark.com
- Snewd
- Gitenberg
- Hoopla
- Overdrive
- Librivox audiobooks
- NASA’s history books
- you can also search multiple libraries near you at the same time with WorldCat