PURPOSE OF REVIEW: Improving HIV testing uptake is essential to ending the HIV pandemic. HIV testing approaches can be opt-in, opt-out or risk-based. This systematic review examines and compares the uptake of HIV testing in opt-in, opt-out and risk-based testing approaches. RECENT FINDINGS: There remain missed opportunities for HIV testing in a variety of settings using different approaches: opt-in (a person actively accepts to be tested for HIV), opt-out (a person is informed that HIV testing is routine/standard of care, and they actively decline if they do not wish to be tested for HIV) or risk-based (using risk-based screening tools to focus testing on certain individuals or sub-populations at greater risk of HIV). It is not clear how the approach could impact HIV test uptake when adjusted for other factors (e.g. rapid testing, country-income level, test setting and population tested). We searched four databases for studies reporting on HIV test uptake. In total, 18,238 records were screened, and 150 studies were included in the review. Most studies described an opt-in approach (87 estimates), followed by opt-out (76) and risk-based (19). Opt-out testing was associated with 64.3% test uptake (I2 = 99.9%), opt-in testing with 59.8% (I2 = 99.9%) and risk-based testing with 54.4% (I2 = 99.9%). When adjusted for settings that offered rapid testing, country income level, setting and population tested, opt-out testing had a significantly higher uptake (+ 12% (95% confidence intervals: 3-21), p = 0.007) than opt-in testing. We also found that emergency department patients and hospital outpatients had significantly lower HIV test uptake than other populations.