N50 is the sequence length such that half of the total bases are in sequences of that length or longer. It is a common summary of assembly or read-length distributions.

Which FASTQ quality encodings are supported?

Phred+33 (Sanger / Illumina 1.8+) and Phred+64 (older Illumina 1.3–1.7). Pick the encoding that matches your data.

Does it validate the file?

Yes. It flags missing '+' separators, sequence/quality length mismatches and malformed records.

FASTA / FASTQ Statistics & Validator

Summarise and validate FASTA or FASTQ: counts, N50, GC, quality.

🔒 Runs entirely in your browser — nothing is uploaded

Summarise and validate FASTA or FASTQ files entirely in your browser: read count, total bases, min/max/mean/median length, N50, GC content and mean Phred quality. A quick way to QC sequencing reads or an assembly without installing command-line tools or uploading sensitive data.

Paste FASTA or FASTQ

Detected format: unknown

How to use the FASTA/FASTQ Stats tool

1Paste or drop in your FASTA or FASTQ content.
2Pick the Phred quality encoding (Phred+33 or Phred+64) for FASTQ.
3Read the summary statistics and any validation warnings.

Frequently asked questions

What is N50?: N50 is the sequence length such that half of the total bases are in sequences of that length or longer. It is a common summary of assembly or read-length distributions.
Which FASTQ quality encodings are supported?: Phred+33 (Sanger / Illumina 1.8+) and Phred+64 (older Illumina 1.3–1.7). Pick the encoding that matches your data.
Does it validate the file?: Yes. It flags missing '+' separators, sequence/quality length mismatches and malformed records.

Learn more

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