We use millions of user-entry salaries from Glassdoor to evaluate how well data from online wage postings compare with more traditional, aggregated data, such as the Quarterly Census for Employment and Wages (QCEW) or household-level data such as the Panel Study of Income Dynamics (PSID). We perform our analysis across industries as well as geographical areas. We find that industry employment shares differ substantially between Glassdoor and QCEW. However, the correlation between industry- and region-specific average salaries in Glassdoor and the QCEW is fairly high. Similarly, the within-industry dispersion in salaries in Glassdoor is fairly close to the dispersion in the PSID.