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Abstract Live bacteria known as probiotics can help the host's health when given in sufficient doses. The use of probiotics in chicken has expanded gradually over the years due to higher demand for antibiotic-free poultry. This systematic study aims to summarize and assess the effects of probiotics on the digestion, immunology, and growth and laying performance, gut histomorphology, and gut microbiota of chicken. An electronic search was conducted using relevant keywords to include literature pertaining to the topic. Under the current commercial production conditions, the performance and gut health of chicken were critically evaluated for 17 regularly used probiotic species. According to the findings, probiotic supplementation may have the following effects: 1. Altering the gut microbiota, 2. Promoting.