---
title: "Filter a multi-record file"
method: POST
path: "/fasta_filter"
tags: ["Files & formats"]
---

# Filter a multi-record file

`POST /fasta_filter`

## Request

- Base URL: `https://seqbench.com/api/v1`
- URL: `https://seqbench.com/api/v1/fasta_filter`
- Auth: none required

Keep a subset of a FASTA file: by length, by a LIST of names (the shape "filter by ID" actually takes — two hundred accessions, not one substring), by a drop list, and by removing records that are the same sequence twice. Every dropped record comes back named with the one rule that removed it, because a count says you lost 88 sequences and not which. Identical sequences are reported whether or not they were asked to be dropped: a folder concatenated twice looks fine until something downstream counts it.

## Request body

- object
  - `input` string, required: A multi-record FASTA.
  - `minLength` integer: Shortest sequence to keep, in residues.
  - `maxLength` integer: Longest sequence to keep.
  - `nameContains` string: Keep a record whose name contains ANY of these, case-insensitively. Separated by commas, spaces or newlines.
  - `nameExcludes` string: Drop a record whose name contains any of these. Applied after the keep list.
  - `dropDuplicateSequences` boolean: Keep only the first record of each identical sequence.

## Response `200`

Tool ran successfully.

- SuccessResponse: Standard success envelope returned by every single-tool call.
  - `ok` unknown, required
  - `tool` string, required: The tool slug that ran.
  - `result` object, required: Tool-specific output object. Its shape depends on the tool — call `GET /{tool}` or see the docs for each tool's fields.
  - `gate` GateResult
    - `pass` boolean, required: True if and only if every hard check passed.
    - `checks` GateCheck[], required
      - `id` string, required
      - `label` string, required
      - `severity` 'hard' | 'soft', required
      - `pass` boolean, required
      - `message` string, required
      - `value` number
      - `threshold` string
    - `notChecked` string[], required: Honest list of what this gate does NOT verify.
  - `provenance` Provenance, required
    - `apiVersion` string, required
    - `tool` union, required: Tool slug, or an array of slugs (one per step) for a workflow.
      - string
      - string[]
    - `generatedAt` string, date-time, required: ISO 8601 timestamp of when the result was generated.

## Other responses

- `400`: Invalid argument or the tool could not run.
- `404`: Unknown tool.
- `429`: Rate limited (metered tools only). Body carries code `rate_limited` and retryable `true`; honor the Retry-After header.
- `503`: A metered tool is momentarily at capacity. The identical request should succeed after Retry-After; body carries code `upstream_unavailable`.

---

[API](https://skmtc.dev/seqbench/apis/seqbench-api.md) · [All operations](https://skmtc.dev/seqbench/apis/seqbench-api/llms.txt) · [OpenAPI document](https://skmtc.dev/seqbench/apis/seqbench-api/revisions/132575216865?raw)