Direct answer
To show an existing size-chart image on a WooCommerce product, save the local WordPress attachment ID, verify it is still a valid image, and render WordPress's responsive image markup inside a native details disclosure at a documented WooCommerce product-summary hook. Render nothing when the attachment or hook is unavailable. Do not copy templates, fetch a remote image, or inject a popup with theme-specific selectors.
StoreFixKit's Size Chart Image for WooCommerce uses that narrow model. Free assigns one image per product. Pro reuses one chart by category or tag and offers three finite placements.
Start with the real artifact
Some merchants already have an approved chart from a manufacturer, designer, or measurement guide. Their job is not to rebuild that chart as HTML. It is to put the finished image beside the right product in a way shoppers can find and open.
WooCommerce's commercial Product Size Charts and Guides covers a broader feature set. Other WordPress.org plugins build chart tables, templates, popups, and assignment systems. Those products may fit merchants who need editable measurements or recommendation workflows.
A focused image helper should not pretend to be a measurement engine. It should make one local image visible and fail quietly when it cannot prove that image is usable.
Use a WordPress attachment ID, not a pasted remote URL
The Media Library already owns local files, metadata, alt text, dimensions, and responsive derivatives. Saving the attachment ID lets WordPress choose an appropriate image size and srcset for the current page.
A pasted external URL can disappear, change content, bypass the site's image controls, or create a third-party request on every product view. StoreFixKit does not fetch, proxy, or validate remote images.
The plugin also should not duplicate the file. The product setting points to the existing attachment; deleting the plugin must not delete the merchant's media.
Why a native inline disclosure is a safer first interface
The HTML details and summary elements provide a built-in disclosure that works with keyboard interaction without a plugin script. The chart opens in the document flow, so the shopper does not lose context or need to dismiss a modal.
A popup or lightbox adds focus management, escape behavior, body scrolling, stacking layers, mobile viewport handling, JavaScript errors, theme conflicts, and accessibility tests. Those can be solved, but they are not necessary for the one-image job.
The inline approach also means there is no hidden overlay if JavaScript fails. If the browser can render the product page, it can render the disclosure.
Responsive image output matters
The container can keep an image within its available width, but the plugin cannot make tiny text inside a bitmap readable. The source chart still needs clear labels, adequate contrast, and a layout tested at a narrow viewport.
WordPress should generate the image markup so the browser receives the attachment's available dimensions and responsive sources. The plugin should never manufacture a URL string when WordPress says the attachment is invalid.
Use the attachment alt text
Alt text should explain the useful content or purpose of the chart, not repeat image or a filename. A merchant can write that text in Media Library. If it is absent, a short escaped label such as Size guide is a safer fallback than an unhelpful empty filename.
Complex charts may still need nearby text that communicates key measurements. An image-only plugin cannot turn a dense visual table into a complete text alternative. Merchants with that requirement should publish accessible product copy or use a tested HTML table system.
What public support complaints teach
WordPress.org support includes reports such as a size chart not appearing and broader support queues for chart plugins. A missing chart can result from assignment rules, invalid images, cache, templates, hook placement, or many interacting display modes.
The lesson is not that every chart plugin has the same bug. It is that a simple product should make absence predictable: no valid local image means no output; no matching product means no output; no supported hook means no forced injection.
Product-specific configuration should win
A chart explicitly selected on a product is the clearest instruction. A reusable category or tag chart should apply only when there is no valid product-specific image.
Pro therefore follows this order:
- valid product-specific Free image;
- otherwise a matching shared chart that is not excepted;
- otherwise no StoreFixKit chart.
This keeps a broad apparel-category assignment from silently replacing a special chart on one product.
Use finite documented placements
Pro offers after price, before add to cart, and after product details. Each corresponds to a public WooCommerce product-summary hook and priority.
An active block or builder template may omit one or more classic hooks. In that case, the safe result is no chart at that position. The plugin should not search the DOM for a price selector, inject after an arbitrary class, or override the template to force visibility.
What the plugin should not do
It should not upload, crop, regenerate, compress, translate, or delete media. It should not replace the product gallery, build measurement tables, calculate a recommended size, open a modal, or add theme-specific integration code.
It also should not change product search, core tabs, price, stock, cart, checkout, or orders. A chart is read-only product information.
Safety and resource boundaries
The frontend needs no plugin JavaScript or stylesheet. The plugin creates no custom table, cron event, telemetry, public remote request, storefront write, or remote image request. It reads one bounded product configuration or one bounded Pro option, then asks WordPress for responsive image markup.
A malformed, deleted, private, or non-image attachment returns no output. Pro or the license API being unavailable cannot stop a saved Free chart from rendering locally.
The Size Chart Image documentation contains the exact image preparation, setup, troubleshooting, accessibility, rollback, and uninstall workflow.
Beginner test checklist
Valid product image
The Size guide summary should appear once and open the selected chart.
Desktop and mobile
The chart should stay inside its content width with no horizontal page overflow.
Keyboard
Tab to the summary and open it with Enter or Space.
Attachment alt text
Inspect the rendered image and confirm the meaningful Media Library alt text appears.
Deleted or invalid image
No broken image, placeholder, remote request, or warning should appear on the storefront.
Shared category or tag
A matching product without its own chart should show the shared Pro chart. An unrelated product should not.
Product-specific override and exception
A valid product image should win over the shared rule. An explicit exception should suppress only the shared chart.
Custom product template
If the selected hook is absent, the plugin should render nothing instead of injecting through selectors.
Update and rollback
Downgrade and return to the current version. Attachment IDs and labels should remain while the Media Library files stay untouched.
Security and support evidence
Only users allowed to edit products should change product charts, and only users who manage WooCommerce should change shared rules. Writes require capabilities, nonces, attachment validation, bounds, and escaped output. WordPress's common plugin issues guide summarizes those review expectations.
Useful support evidence includes the product and attachment IDs, image format and dimensions, alt text, selected placement, assignment and exception IDs, theme or template, WooCommerce and plugin versions, and desktop/mobile screenshots. Do not send credentials, customer data, private media URLs, or full license keys.
Rollback boundary
Keep database and package backups. Deactivate Pro and Free, install the previous known-good versions, activate Free before Pro, and test product-specific, shared, excepted, missing-image, mobile, and keyboard cases. Since the plugin never edits attachments or templates, rollback should not require repairing media or product data.
FAQ
Does this build a size table?
No. It displays a finished image already stored in the Media Library.
Does it use a popup?
No. It uses a native inline disclosure and loads no frontend JavaScript.
Will uninstall delete my image?
No. It removes only StoreFixKit's product assignment and Pro settings, not Media Library attachments.
What if my theme omits the selected hook?
The chart does not render. StoreFixKit does not replace the template or inject by selector.
What happens when Pro expires?
Product-specific Free charts continue working. Shared Pro assignments become unavailable without modifying media files.
Focused plugin
Use the one-job implementation.
Choose one existing Media Library image and show it as a keyboard-operable inline size guide on selected WooCommerce products.