Should I use hyphens or underscores in filenames?

Hyphens. Google explicitly treats hyphens as word separators (so "best-running-shoes.jpg" is read as 3 keywords) but treats underscores as part of one word ("best_running_shoes.jpg" is read as one token).

How long should an image filename be?

3-5 words is the sweet spot. Long enough to be descriptive ("blue-running-shoes-women.jpg") but short enough to scan. Avoid "DSC_0042.jpg" or "image1.jpg" — these signal nothing to Google.

Does file extension matter for SEO?

Yes, indirectly. .jpg/.jpeg for photos, .png for graphics with transparency, .webp for modern compression, .svg for vectors. Google handles all of these; your choice affects file weight and page speed, which feeds back into ranking.

Can I use uppercase letters?

Yes, but lowercase is preferred. URLs are case-sensitive on most servers; "Image.jpg" and "image.jpg" can be different files. Stick to lowercase to avoid 404s when content moves between systems.

Should I include keywords in image filenames?

Yes, descriptively. The filename "blue-leather-handbag.jpg" tells Google what the image shows. Keep it natural — "best-cheap-leather-handbag-2026.jpg" reads spammy and may underperform a clean "leather-handbag.jpg".

Are special characters allowed?

Avoid them. Spaces become %20 in URLs and look ugly; commas, parentheses, and accented characters trigger encoding issues. Stick to a-z, 0-9, and hyphens.

Does this affect ranking directly?

Indirectly. Filename is one of ~10 signals Google uses to understand image content (alt text, surrounding copy, page topic, schema, etc.). Optimizing filenames is a small lever but it stacks with other image SEO work.

Should I rename existing images?

For pages that drive significant traffic, yes — but redirect old URLs to new ones to avoid breaking external links. For low-traffic images, the cost-benefit usually does not justify the rename.

What is "kebab-case"?

Words separated by hyphens, all lowercase: "my-product-photo.jpg". This is the SEO-preferred filename format. Other cases (camelCase, snake_case) are valid but less effective for Google Images.

How does this compare to alt text?

Filename + alt text together describe the image. Filename describes the file ("blue-running-shoes.jpg"), alt text describes the visual content ("Blue Adidas running shoes on a wooden floor"). Both matter; both should mention relevant keywords naturally.

Can I batch-check filenames?

This tool checks one at a time. For batch operations, export your image library to CSV and check filenames programmatically against the same rules (hyphens, lowercase, length).

Is filename more important than alt text?

No. Alt text is a stronger ranking signal because it directly describes the image content. But filename is easier to fix and stacks with alt text. Optimize both for full image SEO.

Free SEO Tool

Free Image Filename SEO Checker

Type any image filename. Get a 0-100 score, Pass/Fail, plus issues, warnings, and rewrite suggestions. Free, instant, no signup.

4.6on G2

4.8on Trustpilot

Used by 35,000+ SEOs

What the Filename SEO Checker does

Image filenames are a small but real ranking signal. "DSC_0042.jpg" tells Google nothing; "blue-leather-handbag.jpg" tells Google what the image shows. The checker validates against best practices and gives a 0-100 score plus actionable issues.

Use it pre-upload (validate before publishing) or to audit existing image libraries (rename the worst offenders if their pages drive traffic).

How to check a filename

Five steps from name to optimized.

Type or paste filename

Include the extension (e.g., my-photo.jpg).

Click Check Filename

The checker validates against SEO best practices.

Read the score

See your 0-100 score, Pass/Fail, and any issues, warnings, or suggestions.

Apply the fixes

Rename the file before upload, or rename in your CMS if already uploaded.

Re-check after rename

Validate the new name to confirm Pass status.

When SEOs and developers use it

Six common workflows.

Pre-upload validation

Run every image filename through the checker before uploading to your CMS. Catch issues before they get baked into URLs.

Image library audit

Audit existing image filenames; rename the worst offenders if their pages drive traffic.

CMS migration cleanup

Migrating to a new CMS is the perfect time to rename images systematically. Run candidates through the checker before importing.

E-commerce product photos

Product images are high-volume. Naming conventions matter for Google Shopping and Image Search.

Stock photo asset library

Downloaded stock photos come with random filenames. Rename before adding to your asset library.

SEO audit deliverable

Audit image filenames as part of a client SEO audit; the score gives you concrete recommendations.

Platform-specific setup guides

How to enforce naming conventions on the platforms most teams use.

WordPress

Use a plugin like Phoenix Media Rename to rename existing images.
Set CMS rules to enforce kebab-case on new uploads.
For new images, rename before upload — the URL is set at upload time.

Webflow

Asset Manager allows renaming on upload.
For CMS-bound images, use the Collection field name (auto-generates from item name).
Audit periodically by inspecting served URLs.

Shopify

Product image filenames are auto-generated from upload. Rename source files before upload.
Theme images are set in liquid templates.
Audit a sample of product URLs to catch naming issues.

Next.js

For static images in /public/, use kebab-case filenames.
For CMS-fetched images, rename at the source.
Run a build-time check to enforce naming conventions in CI.

Bulk rename via script

For large libraries, use a bash one-liner: for f in *.jpg; do mv "$f" "$(echo "$f" | tr "_ " "--" | tr "[:upper:]" "[:lower:]")"; done
Test on a sample first.
For CMS-managed assets, the rename should happen via the CMS API to preserve URL mappings.

Grigora vs. other filename checkers

Side-by-side feature comparison.

Capability	Grigora	Screaming Frog	SEMrush	Free generators	Manual
Free + unlimited	Yes	Yes	Free trial	Yes	Manual
Score + Pass/Fail	Yes	No	Yes	No	No
Issues, warnings, suggestions	All three	Issues only	Yes	No	Manual
Detects all common errors	Yes	Partial	Yes	No	Manual
No signup	Yes	Yes	Account required	Yes	Yes
Multi-language	Yes	English only	Yes	English only	N/A
Result speed	<1 sec	<1 sec	<3 sec	<1 sec	Manual
Privacy: no file retention	Yes	N/A	Stored	N/A	Yes

Common errors and how to fix them

Eight issues teams hit when naming image files.

Filename has spaces

Cause: Default camera or design-tool exports include spaces.

Fix: Replace spaces with hyphens. "My Photo.jpg" becomes "my-photo.jpg".

Filename has UPPERCASE letters

Cause: Operating system case-preservation.

Fix: Convert to lowercase before upload.

Filename has special chars (commas, parens)

Cause: Common in CMS-uploaded files.

Fix: Strip special chars; use only a-z, 0-9, and hyphens.

Filename is "DSC_0042.jpg"

Cause: Default camera or phone naming.

Fix: Rename descriptively before upload — "sunset-beach-california.jpg".

Filename is too long (50+ chars)

Cause: Trying to stuff too many keywords.

Fix: Cut to 3-5 descriptive words.

Filename is too short ("a.jpg")

Cause: Lazy naming.

Fix: Use at least 2-3 descriptive words.

Filename uses underscores

Cause: snake_case habit from code.

Fix: Convert underscores to hyphens for SEO.

Filename has the wrong extension

Cause: PNG saved as .jpg or vice versa.

Fix: Re-export with the correct format and matching extension.

Original data from our 2026 filename audit

Across 3,000 random image URLs.

64%

% of image URLs we sampled with at least one filename SEO issue

Underscores instead of hyphens

Most common issue

38%

% of files using descriptive names (vs. DSC_xxxx)

Median character count of well-rated filenames

Frequently asked questions

Twelve answers about image filename SEO.

Related free tools

Other utilities that pair with the Filename SEO Checker.

Validate a filename right now

Type, score, fix. Free, unlimited, no signup.

Try the Filename Checker