An online tool for analysing large amounts of small RNA-Seq data and acquiring their modifications profile. It allows the mapping of the input sequences to miRBase in order to decipher the miRNA expression content in the input samples. It also identifies any modifications related with the input sequences. The modification types that are being supported include all types of 3’-modifications (e.g. uridylation, adenylation, ADAR editing), 5’-modifications and also internal modifications (SNPs and ADARs). Chimira expects as an input FASTQ or FASTA files containing adapter and/or barcode stripped small RNA-Seq data.