In most Uralic languages, if spreading is not blocked by a segment, the harmonic domain is the word, irrespectively of its length. (Occasionally, it can be even longer, cf. §4.3.) 

The harmonic domain can be shorter than the word in some Finnic languages and dialects. Wiik (1989 :60–61, 63–64) reports that VH is restricted to the first three syllables in most Veps dialects, and it can reach the fourth syllable in some of them. Analyzing the decaying harmony in Estonian dialects, Wiik (1988: 189–192) also concludes that the shortening of the harmonic domain can be a symptom of the weakening of VH. However, he does not provide data about the length of the harmonic domain in different dialects. According to Tanning (1961: 32–34), in the Mulgi dialect of Estonian, the length of the harmonic domain can be two or three syllables depending on the subdialect. However, the texts published by her show that the harmonic domain can reach the third syllable in every subdialect (cf. §4.2..)

In Udmurt, the spreading of F is optional, and usually it does not reach the syllables distant from the initial one (see also §4.2).

Vértes (1977) found that in Southern Khanty, there are no words longer than four syllables with exclusively B vowels, although there are five and six syllable words with exclusively F vowels (however, their number is also very low, less than 0.05–0.35% of all words in different subdialects).