How to add alt text and optimise your images for SEO in WordPress

Why image optimisation matters for your website

Images account for over 60% of your website's total size, making them the biggest factor affecting your site's loading speed. In 2025, with Google's continued emphasis on Core Web Vitals and user experience, properly optimised images aren't just nice-to-have – they're essential for business success.

The business impact of image optimisation

According to recent studies, visitors will wait an average of just 8 seconds for a website to load in 2024. For small businesses, this means:

Higher conversion rates: Faster sites convert better – even a 1-second delay can reduce conversions by 7%
Better search rankings: Google uses page speed as a ranking factor
Improved accessibility: Proper alt text makes your site usable for visually impaired customers
Increased mobile traffic: Mobile users are even more impatient with slow-loading images
Lower hosting costs: Smaller images reduce bandwidth usage

What Google Images means for your business

Over 20% of all Google searches happen on Google Images. When your images are properly optimised with descriptive file names and alt text, they can appear in image search results, bringing you additional traffic that many businesses completely miss.

What is alt text and why is it crucial?

Alt text (alternative text) is a short description of an image that helps both people and search engines understand what the image shows.

Who benefits from alt text?

Visually impaired users: Screen readers speak the alt text aloud
Users with slow connections: Alt text displays when images fail to load
Search engines: Google uses alt text to understand your images and page content
Voice search users: Alt text helps voice assistants understand your content

Legal requirements you should know about

In 2025, accessibility isn't optional. The Web Content Accessibility Guidelines (WCAG) 2.1 Level AA is increasingly referenced in legal cases. Proper alt text is a requirement, not a suggestion, and failing to provide it can expose your business to legal risks.

Getting your image file names right

Before you even upload an image to WordPress, you need to give it a proper file name. This is your first opportunity to help search engines understand what your image shows.

Best practices for image file naming

Do this:

Use descriptive words: "red-leather-handbag.jpg" instead of "IMG_1234.jpg"
Separate words with hyphens: "manchester-office-building.jpg" not "manchesterofficebuilding.jpg"
Keep it concise: 3-5 words maximum
Use lowercase: Easier to manage and more consistent
Include your target keyword: If relevant and natural

Avoid this:

Generic names like "image1.jpg" or "photo.png"
Special characters or spaces
Random numbers or codes
Keyword stuffing

Quick file naming checklist

Before uploading any image, ask yourself:

Does the filename describe what's in the image?
Would someone else understand what this image shows from the filename alone?
Are the words separated by hyphens?
Is it concise but descriptive?

How to add alt text in WordPress (step-by-step)

WordPress makes adding alt text straightforward, whether you're using the classic editor or the modern Gutenberg Block Editor. Here's how to do it properly:

Method 1: Adding alt text in the Block Editor (Gutenberg)

Click on your image to select it
Look for the "Block" tab in the right sidebar
Find the "Alt text (alternative text)" field
Enter your descriptive alt text
Click "Update" or "Publish" to save your changes

Method 2: Adding alt text through the Media Library

Go to Media > Library in your WordPress dashboard
Click on the image you want to edit
In the attachment details popup, find the "Alt Text" field
Enter your alt text
Click "Update" to save

Method 3: Adding alt text when uploading new images

When uploading a new image, WordPress shows the attachment details
Fill in the "Alt Text" field immediately
Complete other fields like caption if needed
Insert the image into your content

Pro tip: Checking existing images

To find images missing alt text on your site, you can use browser tools or accessibility plugins. Simply right-click on an image and select "Inspect" to see if the alt attribute is present and populated.

Writing effective alt text that works

Good alt text balances being descriptive for accessibility while being useful for SEO. Here's how to write alt text that serves both purposes:

The golden rules of alt text

1. Keep it concise but descriptive (under 125 characters)

Screen readers typically stop reading alt text at 125 characters. Aim for 7-10 words that capture the essential information.

2. Describe what you see, not what you think

Focus on observable facts rather than interpretations or emotions.

3. Consider the context

How does the image relate to the surrounding content? Tailor your description accordingly.

4. Include keywords naturally

If your target keyword fits naturally, include it – but never force it.

Alt text examples that work

Product photography:

Bad: "Product image"
Good: "Red leather handbag with gold buckle detail"

Team photos:

Bad: "Staff"
Good: "Three customer service team members smiling in office"

Screenshots:

Bad: "Screenshot"
Good: "WordPress dashboard showing plugin installation screen"

Decorative images:

Bad: "Image"
Good: Leave alt text empty (alt="") for purely decorative images

What not to include in alt text

Don't start with "Image of" or "Picture of" – it's redundant
Don't describe the image format or size
Don't repeat information that's already in the surrounding text
Don't keyword stuff or include irrelevant terms
Don't use alt text for decorative images that add no information

Using image captions and descriptions effectively

Beyond alt text, WordPress offers additional fields that can enhance your image SEO and user experience:

Image captions

Captions appear below your image and may be visible to visitors, depending on your theme. Not all themes are set up to show captions. If yours does then they're perfect for:

Adding context that supports your content
Including credits or source information
Providing additional keywords naturally
Enhancing user engagement

Image descriptions

Descriptions are used when someone clicks through to the image attachment page. While less commonly used, they can be valuable for:

Detailed explanations of complex images
Background information or stories
Technical specifications for product images
Additional SEO content
Helping you to search for relevant images in the backend of your site

Title text (use sparingly)

Title text appears when someone hovers over an image. In 2025, it's less important for SEO and can actually interfere with accessibility, so use it sparingly or not at all.

Best practice workflow

Always add alt text – this is non-negotiable
Add captions when they add value – don't caption every image
Use descriptions for detailed context – when the image needs explanation
Skip title text – unless specifically needed for functionality

Modern image formats: WebP and AVIF in 2025

Traditional JPEG and PNG files are being superseded by modern formats that offer much better compression. In 2025, using these new formats is becoming essential for competitive website performance.

Understanding the new formats

WebP format

Benefits: 25-35% smaller than JPEG, supports transparency like PNG
Browser support: Excellent – supported by all modern browsers
Best for: Most websites transitioning from JPEG/PNG

AVIF format

Benefits: Up to 50% smaller than WebP, excellent quality retention
Browser support: Good and growing rapidly
Best for: High-performance sites, image-heavy content

How to implement modern formats in WordPress

WordPress 5.8+ supports WebP natively, but you'll want to use a plugin for broader format support and automatic conversion:

Recommended plugins for format conversion:

Smush Pro: Automatic WebP and AVIF conversion with CDN
Optimole: Cloud-based conversion and delivery
ShortPixel: Advanced compression with multiple format support
WP-Optimize: Good all-in-one option for smaller sites

Implementation strategy for small businesses

Start with WebP: It's universally supported and provides immediate benefits
Test your site: Ensure all images display correctly across devices
Monitor Core Web Vitals: Track improvements in loading speed
Consider AVIF: For image-heavy sites, add AVIF support for additional savings

Image optimisation for Core Web Vitals

Google's Core Web Vitals are essential ranking factors that measure user experience. Images significantly impact these metrics, particularly Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS).

Key strategies

Lazy loading (but do it right)

WordPress enables lazy loading by default, but you need to be strategic:

Never lazy load above-the-fold images: This hurts LCP scores
Prioritise hero images: Load them immediately
Use proper placeholders: Prevent layout shifts

Responsive images

WordPress automatically creates multiple image sizes, but ensure they're working properly:

Check that srcset attributes are present
Verify different sizes load on different devices
Don't disable WordPress's responsive image features

Image sizing and dimensions

Always specify image dimensions to prevent layout shifts:

Set width and height attributes
Use aspect-ratio CSS for flexible layouts
Avoid images that are much larger than their display size

Measuring your improvements

Use these tools to monitor your progress:

Google PageSpeed Insights: Free tool for Core Web Vitals scoring
Google Search Console: Real-world performance data
GTmetrix: Detailed performance analysis
Chrome DevTools: Advanced debugging and testing

Accessibility and legal considerations

In 2025, website accessibility isn't just about being inclusive – it's increasingly a legal requirement. Proper image optimisation plays a crucial role in meeting accessibility standards.

WCAG 2.1 Level AA requirements

The Web Content Accessibility Guidelines are the international standard, and Level AA is commonly referenced in legal cases:

Essential requirements for images:

Text alternatives (1.1.1): All informative images must have meaningful alt text
Contrast ratios (1.4.3): Text in images must meet minimum contrast requirements
Resize text (1.4.4): Images of text should be avoided where possible
Images of text (1.4.5): Use actual text instead of images of text when possible

When to leave alt text empty

Decorative images that don't add information should have empty alt attributes (alt=""). This tells screen readers to skip them:

Background patterns or textures
Decorative borders or spacers
Images that are purely aesthetic
Images where the information is already conveyed in nearby text

Testing your accessibility

Regular testing ensures you're meeting accessibility standards:

Automated tools: WAVE, axe DevTools, Lighthouse accessibility audit
Manual testing: Navigate your site using only the keyboard
Screen reader testing: Use NVDA (free) or VoiceOver (Mac) to experience your site
Professional audits: Consider hiring accessibility experts for important sites

Legal landscape in 2025

Accessibility lawsuits continue to increase. While specific requirements vary by jurisdiction, following WCAG 2.1 Level AA provides strong legal protection and ensures your site serves all users effectively.

Tools to automate your image optimisation

For small businesses managing multiple images, automation tools can save hours of work while ensuring consistent optimisation.

WordPress plugins for automation

For bulk alt text generation:

ImageSEO (AI-powered): Uses artificial intelligence to generate alt text automatically
BIALTY: Creates alt text from page titles and Yoast focus keywords
WP Accessibility: Helps identify and fix missing alt text

For comprehensive optimisation:

Smush Pro: Compression, format conversion, and CDN delivery
Optimole: Cloud-based optimisation with automatic format serving
WP-Optimize: All-in-one performance including image optimisation
ShortPixel: Advanced compression with WebP/AVIF support

External tools for preparation

Before uploading to WordPress:

TinyPNG: Quick compression for JPEG and PNG files
Squoosh (by Google): Browser-based tool for format conversion
ImageOptim (Mac): Drag-and-drop compression tool
Photopea: Free browser-based image editor

Setting up an automated workflow

Choose your plugin: Pick one comprehensive solution rather than multiple competing plugins
Configure settings: Set up automatic compression and format conversion
Bulk optimise existing images: Process your current media library
Set up monitoring: Use tools to track performance improvements
Train your team: Ensure everyone knows how to add proper alt text

Common mistakes to avoid

Even well-intentioned efforts can go wrong. Here are the most common image optimisation mistakes we see small businesses make:

Alt text mistakes

Using filename as alt text: "IMG_1234.jpg" tells users nothing useful
Keyword stuffing: "Best plumber Manchester plumbing services emergency plumber" is spam
Being too vague: "Man" instead of "Plumber fixing kitchen sink"
Repeating nearby text: If your heading says it, your alt text doesn't need to
Alt text for decorative images: Screen readers don't need to announce decorative elements

Technical mistakes

Uploading massive files: Don't rely on WordPress to resize 10MB photos
Wrong file formats: Using PNG for photographs or JPEG for logos with transparency
Ignoring mobile: Your images must work on small screens
Blocking lazy loading: Don't disable WordPress's built-in lazy loading
Missing dimensions: Always specify width and height to prevent layout shifts

SEO mistakes

Ignoring image search: Millions of searches happen on Google Images daily
Poor file organisation: Random folder structures make images hard to manage
Duplicate alt text: Every image should have unique, descriptive alt text
Forgetting image sitemaps: Help search engines find your images

Quick self-audit checklist

Review your last 10 blog posts and check:

Do all images have meaningful alt text?
Are file names descriptive?
Do images load quickly on mobile?
Are you using modern image formats where possible?
Do decorative images have empty alt attributes?

Measuring your optimisation success

Image optimisation should deliver measurable improvements in site performance, user experience, and search visibility. Here's how to track your progress:

Performance metrics to monitor

Core Web Vitals (essential)

Largest Contentful Paint (LCP): Should be under 2.5 seconds
First Input Delay (FID): Should be under 100 milliseconds
Cumulative Layout Shift (CLS): Should be under 0.1

Additional performance metrics

Page load time: Aim for under 3 seconds
Image load time: Track how quickly images appear
Total page size: Monitor reduction in bandwidth usage
Mobile performance: Ensure improvements work on all devices

SEO and traffic metrics

Image search traffic: Monitor visitors from Google Images
Overall organic traffic: Better performance can improve rankings
Bounce rate improvements: Faster sites keep visitors longer
Conversion rate changes: Speed improvements often boost conversions

Accessibility metrics

Alt text coverage: Percentage of images with proper alt text
Accessibility score: Use tools like Lighthouse or WAVE
Screen reader testing: Regular manual testing with assistive technology

Tools for ongoing monitoring

Google Search Console: Free performance data and Core Web Vitals
Google Analytics: Traffic and user behaviour insights
PageSpeed Insights: Regular performance testing
GTmetrix: Detailed technical analysis
Hotjar or similar: User experience and interaction data

Creating a monitoring schedule

Weekly: Check Google Search Console for Core Web Vitals alerts
Monthly: Run full PageSpeed Insights tests on key pages
Quarterly: Comprehensive accessibility audit and image review
After major updates: Test performance when adding new content or plugins

Setting realistic improvement targets

For small businesses, aim for these improvements within 3 months of implementing image optimisation:

20-40% reduction in total page size
1-2 second improvement in load times
90+ score on PageSpeed Insights (mobile and desktop)
100% alt text coverage on informative images
Green Core Web Vitals scores in Google Search Console

Conclusion: Your image optimisation action plan

Image optimisation is about more than just making your website faster – it's about creating an inclusive, high-performing digital presence that serves all your customers and ranks well in search engines.

Your immediate action plan

Audit your current images: Check which images lack alt text and identify performance issues
Install an optimisation plugin: Choose one comprehensive solution like Smush Pro or Optimole
Bulk optimise existing images: Process your current media library
Create a workflow: Establish processes for future image uploads
Train your team: Ensure everyone understands alt text best practices
Monitor and measure: Set up regular performance tracking

Long-term strategy

Image optimisation isn't a one-time task. As your business grows and web standards evolve, maintain your competitive edge by:

Staying current with new image formats and technologies
Regularly reviewing and updating alt text for accuracy
Monitoring Core Web Vitals performance
Keeping accessibility at the forefront of your digital strategy

The bottom line

Properly optimised images with thoughtful alt text can significantly improve your website's performance, accessibility, and search engine visibility. For small businesses operating on tight margins, these improvements can translate directly into better customer experiences and increased revenue.