Probably the product of (1) multiple changes in "best practices" data formats over 30 years (XML seems to be the format de jure), (2) optimizing for the filer a

Probably the product of (1) multiple changes in "best practices" data formats over 30 years (XML seems to be the format de jure), (2) optimizing for the filer and (3) diversity of filing data. Agreed it would be ideal if they were all similarly structured, but they have another set of stakeholders on whom they are imposing essentially a tax -- the filers themselves -- who have a legitimate gripe any time the SEC imposes a switching cost. It's easy to dismiss those gripes, but the vast majority of these filers aren't GOOG-sized. Many are very small, and those costs can be non-trivial to them. Edit: Worth mentioning here that EDGAR's ease of use makes sites like BamSEC simple to create. Probably EDGAR's time is best spent focusing on the institutional intermediary. That allows competition to iterate on the best UX/UI for browsing these filings without imposing the cost on the filers themselves as discussed above.