This technical report describes the implementation and use of ChildFreq, a tool for assessing lexical norms of children from one to seven years old. As the name implies, ChildFreq works by extracting word frequencies from a large corpus of child language. These can then be ordered by age or mean length of utterance, and it is also possible to split the data by the children’s gender. A query of words to count the frequency of produces both a line chart and a table with more detailed information. The child language data is taken from the English part of the CHILDES database 1 and comprises more than 5,000 transcriptions,a total of ≈ 3, 500, 000 word tokens. The children’s ages range from six months to seven years, with most children being three years old. ChildFreq is freely available online at