---
title: Is This DOI Valid? Scholarly Identifier Check | Scholar Sidekick
description: Enter one DOI, PMID, ISBN, arXiv ID, or scholarly URL. See whether it is well-formed and whether it resolves to a real publication. Single-ID check.
doc_version: "1.0"
last_updated: "2026-05-18"
---

# Identifier Validator

> HTML version: https://scholar-sidekick.com/tools/identifier-validator

Enter a single scholarly identifier (DOI, PMID, PMCID, arXiv ID, ISBN, ISSN, ADS bibcode, or WHO IRIS URL) and check two things in one pass: is it well-formed syntactically, and does it resolve to a real publication in the canonical registry.

## What this tool does

Runs the identifier through Scholar Sidekick's regex validator first (does it match the structural rules for its claimed type) then attempts to resolve it against the appropriate registry. Returns a verdict: `valid + resolvable`, `valid but not resolvable` (well-formed but the registry has no record), or `malformed` (fails the structural check).

## How to use

1. Open [the tool](https://scholar-sidekick.com/tools/identifier-validator).
2. Paste the identifier.
3. Read the verdict. `Valid but not resolvable` is the most common red flag for fabricated citations: the syntax fits, but no paper exists at that ID.

## Programmatic access

The validation is implicit in every identifier-accepting endpoint: `/api/format`, `/api/format/stream`, `/api/export` all return a structured error if the identifier is malformed or fails to resolve. The [scholar-sidekick MCP](https://scholar-sidekick.com/mcp) returns the same diagnostics.

## Related tools

- [DOI Lookup](https://scholar-sidekick.com/tools/doi-lookup) - full metadata if the identifier resolves
- [Identifier Detector](https://scholar-sidekick.com/tools/identifier-detector) - bulk extraction from a text block
- [Citation Verifier](https://scholar-sidekick.com/tools/citation-verifier) - the stronger check: does the claimed citation match the paper at its identifier?
- [Free tools index](https://scholar-sidekick.com/tools) - all citation tools

## Sitemap

See the full [sitemap](https://scholar-sidekick.com/sitemap.md) for all pages.