Separate editable labels from evidence stored in the file header. The checker records the selected filename extension and browser-provided MIME type, then reads the RIFF and WEBP signatures from the first twelve bytes so mismatches are visible in one report.
How to use MIME & Magic Checker
- Select a suspected WebP file even when its extension or MIME label may be misleading.
- Run the check and compare extensionMatches, mimeMatches, magicIsWebP, ASCII signatures, and raw header bytes.
- Use the structural validator next when the signatures match but corruption, chunk bounds, or decoder compatibility remains in question.
What this tool is good at
When to use MIME & Magic Checker
Investigate file identity signals from actual bytes
Diagnose extension, MIME, and actual-header disagreements before routing a file through a decoder, CMS, test fixture, or security review. Use the selected WebP container as evidence instead of trusting only a filename, a browser preview, a rounded file-size label, or an assumption about what an exporter usually writes.
Prepare a reviewable metadata handoff
Compare the .webp suffix and browser MIME label with literal RIFF and WEBP signatures, then run deeper structural validation when the family signature matches. Keep the local report or focused derivative with the related privacy review, preservation record, color decision, publishing ticket, or engineering investigation so another person can repeat the check.
Inspect sensitive assets without an upload
Work with client media, personal photographs, research imagery, unreleased campaigns, and internal diagnostics in the current browser tab without creating a remote image-processing job.
How to choose the right settings
Define the decision before reading the result
Diagnose extension, MIME, and actual-header disagreements before routing a file through a decoder, CMS, test fixture, or security review. Decide whether the goal is identification, privacy, preservation, interoperability, print planning, or container debugging because the same stored field can have different consequences in each workflow.
Separate a stored claim from proven reality
Compare the .webp suffix and browser MIME label with literal RIFF and WEBP signatures, then run deeper structural validation when the family signature matches. Metadata can be missing, stale, edited, malformed, application-specific, or inconsistent with pixels; verify important conclusions against the authoritative record and destination application.
Retain and verify the original
Magic bytes identify a container family only; they cannot validate every chunk, prove benign content, guarantee decoder support, or replace a maintained security boundary. Keep the original until the downloaded report or derivative has been reopened, compared, and accepted by the person responsible for publishing or preservation.
Practical workflow and output details
The browser reads the first twelve bytes and reports ASCII and hexadecimal evidence without decoding pixels or trusting a visitor-editable label as authoritative. Processing uses bounds-checked RIFF and TIFF reads, typed arrays, local Blob output, and Canvas only when visible orientation must be normalized; selected image bytes are never posted for processing.
Magic bytes identify a container family only; they cannot validate every chunk, prove benign content, guarantee decoder support, or replace a maintained security boundary. Government and institutional research links are presented as supporting references for format terminology and risk context, not as endorsements of PicConverters or proof that one focused tool satisfies every policy.
Format behavior and limitations
A correct RIFF/WEBP signature identifies the container family but does not prove every chunk is valid, the image decodes safely, or the content is trustworthy.
Browser MIME values can be inferred from a filename or selection context, so they are reported as labels rather than treated as authoritative.
Government and research sources
These references support the format facts, metadata terminology, and privacy context explained on this page. They do not endorse PicConverters.
WebP container identification, RIFF structure, signatures, and optional EXIF, XMP, and ICC chunks.
Research context for evidence-based file identification rather than relying on a filename alone.
Frequently asked questions
What are WebP magic bytes?
WebP starts with RIFF, a little-endian size, and WEBP at bytes 8–11.
Can a .jpg file really contain WebP?
Yes. Extensions can be changed independently from bytes; the checker makes that mismatch explicit.
Does a matching signature mean the file is valid?
No. Run the WebP validator for complete top-level RIFF bounds and feature checks.
Related WebP tools
WebP Validator
Validate RIFF bounds, image payloads, animation structure, dimensions, and feature-flag consistency without altering the file.
Header Parser
Parse the RIFF header and every top-level WebP chunk offset, payload length, and alignment byte without decoding pixels.
WebP File Analyzer
Create a detailed local report covering WebP encoding, dimensions, chunks, payload bytes, overhead, animation, alpha, and metadata.