The language support is quite impressive with support for latin, CJK and even indic scripts. Notable omissions include RTL scripts like Arabic and Hebrew.
From: https://support.google.com/faqs/faq/6188721
At the moment Google Handwriting Input supports 82 languages: Afrikaans, Albanian, Azerbaijani, Basque, Belarusian, Bengali, Bosnian, Bulgarian, Cantonese, Catalan, Cebuano, Chinese, Chinese (Simplified), Chinese (Traditional), Croatian, Czech, Danish, Dutch, English, Esperanto, Estonian, Filipino, Finnish, French, Galician, German, Greek, Gujarati, Haitian, Hindi, Hmong, Hungarian, Icelandic, Indonesian, Irish, Italian, Japanese, Javanese, Kannada, Khmer, Korean, Kurdish, Kyrgyz, Lao, Latin, Latvian, Lithuanian, Macedonian, Malagasy, Malay, Malayalam, Maltese, Maori, Marathi, Mongolian, Nepali, Norwegian, Nyanja, Odia, Polish, Portuguese, Punjabi, Romanian, Russian, Serbian, Sinhala, Slovak, Slovenian, Somalian, Spanish, Sundanese, Swahili, Swedish, Tamil, Telugu, Thai, Turkish, Ukrainian, Vietnamese, Welsh, Xhosa, Zulu
From: https://support.google.com/faqs/faq/6188721
At the moment Google Handwriting Input supports 82 languages: Afrikaans, Albanian, Azerbaijani, Basque, Belarusian, Bengali, Bosnian, Bulgarian, Cantonese, Catalan, Cebuano, Chinese, Chinese (Simplified), Chinese (Traditional), Croatian, Czech, Danish, Dutch, English, Esperanto, Estonian, Filipino, Finnish, French, Galician, German, Greek, Gujarati, Haitian, Hindi, Hmong, Hungarian, Icelandic, Indonesian, Irish, Italian, Japanese, Javanese, Kannada, Khmer, Korean, Kurdish, Kyrgyz, Lao, Latin, Latvian, Lithuanian, Macedonian, Malagasy, Malay, Malayalam, Maltese, Maori, Marathi, Mongolian, Nepali, Norwegian, Nyanja, Odia, Polish, Portuguese, Punjabi, Romanian, Russian, Serbian, Sinhala, Slovak, Slovenian, Somalian, Spanish, Sundanese, Swahili, Swedish, Tamil, Telugu, Thai, Turkish, Ukrainian, Vietnamese, Welsh, Xhosa, Zulu