| reads | Yes | the reads to trim, as FASTQ - quality lines are required, because both halves of this need them. | |
| _files | No | The project: record references shaped like _subject. Their records become library documents a tool names in sequences/parts/document; a trace or alignment is found by file name. | |
| adapter | No | the adapter sequence to remove. Unset means quality trimming only. Illumina TruSeq is AGATCGGAAGAGCACACGTCTGAACTCCAGTCAC and Nextera is CTGTCTCTTATACACATCT. | |
| _subject | No | The record to act on: exactly one of sequence, accession (+source), sample (an id from list_samples) or file ({name, text} or {name, base64}); record_index picks one record of several. | |
| min_length | No | reads shorter than this after trimming are COUNTED as too short, not removed - this tool does not filter. 0 reports none. Advanced. | |
| min_overlap | No | an adapter overlap shorter than this is ignored. Low values trim real bases by chance - at 1, a read ending in the adapter's first base is 'trimmed'. Advanced. | |
| adapter_kind | No | which end the adapter sits at. A read running off the end of its insert hits the 3' adapter, which is why that is the default. | three_prime |
| phred_offset | No | quality encoding: 33 for every modern FASTQ, 64 only for pre-1.8 Illumina. Advanced. | |
| max_error_rate | No | errors allowed in the adapter match, as a fraction of the overlap. cutadapt's own default. Advanced. | |
| quality_cutoff_back | No | quality cutoff for the 3' end, where quality decays with cycle number. 0 is off; 20 is the usual choice. NOT a threshold on individual bases - see the description. | |
| quality_cutoff_front | No | quality cutoff for the 5' end, which fails for different reasons than the 3' end and so takes its own number. 0 is off, and off is the usual answer. Advanced. | |