FASTQ Quality Viewer
Analyze and visualize sequencing quality from FASTQ files. Perfect for NGS data quality control.
✓ Quality score visualization✓ Per-base statistics✓ Privacy-protected
FASTQ Data Input
Quality encoding: Phred+33
0 sequences detected
Understanding FASTQ Quality Scores
What are Quality Scores?
Quality scores (Q-scores) represent the confidence that a sequenced base is correct.
- • Q10 = 90% accuracy (1 in 10 error rate)
- • Q20 = 99% accuracy (1 in 100 error rate)
- • Q30 = 99.9% accuracy (1 in 1000 error rate)
- • Q40 = 99.99% accuracy (1 in 10000 error rate)
FASTQ Format
@sequence_identifier
ATCGATCGATCG
+optional_description
IIIIIIIIIIII
Each symbol in line 4 represents the quality score for the corresponding base in line 2.
Quality Control Guidelines
Excellent Quality
- • Average Q > 30
- • Q30 bases > 85%
- • No quality drop-off
- • Ready for analysis
Good Quality
- • Average Q > 25
- • Q20 bases > 90%
- • Minor quality issues
- • May need trimming
Poor Quality
- • Average Q < 20
- • High low-quality bases
- • Requires preprocessing
- • Consider re-sequencing