Free CompTIA Study Guides
Free, no-login reference guides for the CompTIA exams people take most: A+, Network+, and Security+. Each guide is a quick-reference cheat sheet with a table or diagram, plain explanations, memory tips, and free sample questions so you can check your understanding before you move on. Pick a topic below to start studying.
Common Port Numbers Cheat Sheet
The TCP/UDP ports every A+, Network+, and Security+ candidate must know — with a reference table and memory tips.
A+ · Network+ · Security+
The OSI Model Explained
All 7 OSI layers broken down with examples, PDUs, and a mnemonic you can actually remember.
Network+
T568A vs T568B Wiring
The exact RJ-45 color order for both standards, the one-pair difference, and crossover cables.
A+
CompTIA Troubleshooting Methodology
The A+ 6-step and Network+ 7-step troubleshooting processes compared, step by step.
A+ · Network+
The 7 Malware Removal Steps
The CompTIA malware removal process (A+ Core 2, objective 2.6) in the correct order.
A+
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Try 3 free sample questions
Questions are visible below. Pick an answer to reveal the correct one and the explanation.
Q1.Which port does HTTPS use?
Q2.At which OSI layer do routers operate?
Q3.What cable results from wiring one end T568A and the other end T568B?
Frequently asked questions
Are these CompTIA study guides really free?
Yes. Every guide on this page is free to read and requires no login. Each one includes a reference table or breakdown, memory tips, and free sample questions. A free CertiTom account adds unlimited practice questions across A+, Network+, and Security+.
Which exams do these guides cover?
They cover CompTIA A+, Network+, and Security+. Port numbers and the OSI model apply to all three; RJ-45 wiring, troubleshooting, and malware removal are weighted toward A+ and Network+. Each guide notes the relevant exam and objective.
Is CertiTom affiliated with CompTIA?
No. CompTIA, A+, Network+, and Security+ are trademarks of CompTIA. CertiTom is an independent study platform and is not affiliated with or endorsed by CompTIA.