Every ingredient line is converted to grams and grouped (butter and oil count as fat; white, brown and liquid sweeteners as sugar), then divided by the flour weight. That baker's percentage is the only comparison that holds across recipes of different sizes.
95% of the 904 ingredient lines got a weight. 63% of those weights were printed by the source; the rest were converted from cups and spoons with standard densities, so treat single recipes as close, not exact. Frosting, glaze, streusel and other toppings are listed on each recipe page but left out of the percentages.
A recipe outside the plausible range for any ingredient is left out rather than allowed to stretch every chart; it is usually a different dish with the same name or a misread line. Of the pages fetched, 313 were left out: 147 with no flour, or none that could be weighed, 105 outside the plausible range on some ingredient (water 63, salt 22, yeast 14, fat 6), 33 with a title that names a different dish, 13 too many lines without an amount, 13 duplicates of other pages, and 2 a listing page, not a recipe page.
Every recipe page links to the original, which is where the method is. Recipe Lab does not republish instructions or photos.