Although the most frequently taken ASVAB test is computer based (the CAT-ASVAB) it’s not available online. You’ll have to go to a military entrance processing station (MEPS) to actually take the test.
However, you can take ASVAB online practice tests on this ASVAB study guide that mimic the format and content of the actual ASVAB test. Taking these online tests can prepare you for the actual test not only by helping you learn the material the test covers but also by building your confidence that you can complete the test within the alloted time.
So, although you can’t take the ASVAB online you can certainly prepare for it online – something Instant ASVAB helps testers do every day!