A small warbler with a pale eyebrow, a dull greenish upperside, a white throat, and yellowish underparts. Sometimes shows a faint central crown stripe, and sometimes an indistinct wingbar. Widespread with small variations, perhaps indicating multiple cryptic species. Singles, pairs, or groups inhabit lowland and hill forest, often accompanying mixed-species flocks. Differs from Arctic, Japanese, and Kamchatka Leaf Warblers in being smaller, yellower underneath, and darker above, and in sometimes showing a central crown stripe. Sings a very variable high-pitched warble mixed with twittering phrases.