When BIMI fails, it often doesn’t fail because of DNS, DMARC, or certificates.
It fails because of the logo.
More precisely: because the logo does not comply with the SVG Tiny Portable / Secure (SVG Tiny P/S) specification required by BIMI.
This article explains what SVG Tiny really is, why mailbox providers enforce it so strictly, and how to prepare a BIMI-compliant logo without costly trial and error.
1. Why BIMI requires SVG Tiny (and not “just SVG”)
SVG is a powerful and flexible format.
Too powerful, in fact.
Standard SVG allows:
- embedded scripts,
- external references,
- fonts and stylesheets,
- animations and filters.
From a mailbox provider’s perspective, this is a security risk.
BIMI therefore mandates SVG Tiny P/S, a restricted profile designed to ensure that:
- logos are safe to render,
- content is fully self-contained,
- and no executable or external behaviour is possible.
In short:
SVG Tiny is not about design freedom — it is about deterministic rendering and security.
2. What exactly is SVG Tiny P/S?
SVG Tiny P/S (Portable / Secure) is a constrained subset of SVG with strict rules:
- No scripting
- No external references
- No fonts
- No raster images
- No animations
- No filters or effects
Everything must be:
- vector-based,
- inline,
- static,
- and predictable.
Mailbox providers fetch and parse the SVG automatically.
Any unsupported element results in silent rejection.
3. Core technical requirements for a BIMI SVG
A BIMI-compliant SVG must meet all of the following:
1. Square aspect ratio
Your logo must be square (1:1 ratio).
Even if your brand logo is rectangular, it must be placed within a square canvas.
Example:
- Valid: 512×512 viewBox
- Invalid: 600×300 viewBox
2. Flat colours only
Gradients, shadows, transparency, and blur effects are not allowed.
Avoid:
- <linearGradient>
- <radialGradient>
- opacity effects
- drop shadows
- filters of any kind
Use solid fills only.
3. No text elements
Text must be converted to vector paths.
Disallowed:
<text font-family=”Arial”>Brand</text>
Required:
- Convert all text to outlines (paths)
- Remove font references entirely
4. No external references
The SVG must be completely self-contained.
Disallowed:
- <image href=”logo.png”>
- external CSS
- external fonts
Everything must live inside the SVG file itself.
5. No embedded metadata or scripts
Remove:
- <script>
- <metadata>
- <foreignObject>
Even harmless metadata can cause rejection.
6. Correct MIME type and hosting
The SVG must be:
- served over HTTPS,
- publicly accessible,
- delivered with the correct MIME type:image/svg+xml
Incorrect headers can break BIMI even if the SVG itself is valid.
4. Common SVG pitfalls that break BIMI
From real-world BIMI deployments, these are the most frequent issues:
❌ “It’s an SVG, so it should work”
Most design tools export full SVG, not SVG Tiny.
That default export almost always contains:
- unsupported elements,
- metadata,
- or effects.
❌ Gradients hidden inside paths
Even when gradients are visually subtle, their presence in the SVG code is enough to invalidate the file.
Always inspect the raw XML.
❌ Fonts not converted to outlines
Leaving text as text is one of the fastest ways to fail BIMI validation.
❌ Invisible elements
Unused layers, hidden shapes, or empty groups can still break validation.
Clean the file aggressively.
❌ Oversized or complex paths
While not explicitly forbidden, extremely complex paths can cause rendering issues.
Keep shapes simple and optimised.
5. Best practices for creating a BIMI-ready SVG
Start from the simplest version of your logo
- Prefer monochrome or two-colour versions.
- Remove decorative effects.
- Focus on recognisability, not detail.
Use vector-native tools carefully
Tools commonly used:
- Adobe Illustrator
- Figma
- Sketch
- Inkscape
But export settings matter more than the tool itself.
Always:
- convert text to outlines,
- flatten layers,
- remove effects,
- and manually inspect the SVG code.
Clean the SVG manually
After export:
- open the SVG in a text editor,
- remove unnecessary tags,
- ensure only allowed elements remain (<svg>, <path>, <rect>, <circle>, etc.).
A smaller, cleaner file is safer.
Validate early and often
Never wait until the end of the BIMI process to validate the SVG.
Validate:
- before certificate issuance,
- before DNS publication,
- before going live.
SVG errors are the most common cause of BIMI delays.
6. Hosting considerations for BIMI SVGs
Where and how you host the SVG matters.
Best practices:
- Host under your own domain (e.g. https://example.com/bimi/logo.svg)
- Ensure HTTPS uses a valid TLS certificate
- Avoid redirects
- Ensure consistent availability
Temporary hosting or CDN misconfigurations can break logo rendering.
7. SVG, VMCs, and certificate validation
When applying for a Verified Mark Certificate (VMC):
- The SVG hash is embedded in the certificate.
- Any change to the SVG after issuance invalidates the certificate.
- Even a whitespace change can break the match.
This means:
The SVG must be final before VMC issuance.
Never “fix” the SVG after the certificate is issued.
8. Testing BIMI SVGs in practice
Before production rollout:
- Validate SVG syntax and allowed elements
- Confirm correct MIME type
- Test HTTPS access from multiple locations
- Confirm no redirects
- Ensure SVG hash stability
BIMI failures are silent — testing is your only safety net.
9. Why BIMI is strict by design
SVG restrictions are not arbitrary.
They exist to:
- prevent logo spoofing,
- ensure predictable rendering across clients,
- and protect mailbox providers and users.
By enforcing SVG Tiny, BIMI guarantees that logos are:
- safe,
- authentic,
- and trustworthy.
10. How Bimimi.io helps teams get SVG right
At Bimimi.io, SVG validation is part of our standard BIMI workflow.
We help:
- designers understand BIMI constraints,
- IT teams validate SVG compliance,
- brands avoid costly rework during VMC issuance,
- and enterprises standardise logo assets across domains.
Our goal is simple:
your logo should appear because it is correct — not because of luck.
Conclusion: the logo is small, the impact is not
SVG Tiny may feel restrictive, especially for designers.
But within those constraints lies something powerful: guaranteed trust at inbox scale.
A correct SVG is not just a technical requirement — it is the visual anchor of your verified brand identity.
Get it right once, and BIMI works exactly as designed.
Learn more about BIMI logo requirements and implementation at: