This snippet adds an "Update SEO Details button" in all media modals, which update SEO alt and description from title - remove special characters and numbers

media-seo-updater.php

<?php
/**
 * Media SEO Updater — Inline JS + AJAX save (single snippet)
 * Paste into Code Snippets or theme/plugin. Runs in admin.
 */

add_action( 'admin_enqueue_scripts', function() {
    // Ensure media scripts are available
    if ( function_exists( 'wp_enqueue_media' ) ) {
        wp_enqueue_media();
    }

    // Print inline JS in footer of admin pages
    add_action( 'admin_print_footer_scripts', function() {
        $ajax_url = admin_url( 'admin-ajax.php' );
        $nonce    = wp_create_nonce( 'msu-save-nonce' );
        ?>
        <script>
        (function($){
            'use strict';

            if (!window.wp || !wp.media || !wp.media.view) return;

            // helper: show admin notice style toast (simple)
            function msuNotify(msg){
                // fallback to alert if not desired
                try {
                    // small unobtrusive message
                    var $n = $('<div>').text(msg).css({
                        position: 'fixed',
                        right: '20px',
                        bottom: '20px',
                        'z-index': 999999,
                        padding: '8px 12px',
                        'background-color': '#0073aa',
                        color: '#fff',
                        'border-radius': '4px',
                        'box-shadow': '0 2px 6px rgba(0,0,0,0.2)'
                    }).appendTo('body').delay(2200).fadeOut(400, function(){ $(this).remove(); });
                } catch(e){
                    alert(msg);
                }
            }

            function injectButton(view){
                if (!view || !view.$el || view.$el.find('.msu-update-seo-btn').length) return;

                var $btn = $('<button type="button" class="button button-primary msu-update-seo-btn" style="margin-top:10px; margin-left:8px;">Update SEO Details</button>');

                $btn.on('click', function(e){
                    e.preventDefault();

                    var model = view.model;
                    if (!model || !model.get) {
                        msuNotify('No attachment data found.');
                        return;
                    }

                    var attachmentId = model.get('id') || model.get('ID') || 0;
                    if (!attachmentId) {
                        msuNotify('Attachment ID not found.');
                        return;
                    }

                    // Read current title from model (prefer model data)
                    var title = String( model.get('title') || '' );

                    // Clean title: remove numbers & special chars, keep letters & spaces
                    var clean = title.replace(/[^a-zA-Z\s]/g,' ').replace(/\s+/g,' ').trim();

                    // Update model (so modal fields update)
                    model.set({
                        alt: clean,
                        caption: clean,
                        description: clean
                    });

                    // Prepare payload for AJAX save
                    var data = {
                        action: 'msu_save_attachment',
                        _ajax_nonce: '<?php echo $nonce; ?>',
                        attachment_id: attachmentId,
                        title: title,           // keep original title for post_title
                        alt: clean,
                        caption: clean,
                        description: clean
                    };

                    // disable button while saving
                    $btn.prop('disabled', true).text('Saving...');

                    $.post('<?php echo $ajax_url; ?>', data)
                        .done(function(res){
                            $btn.prop('disabled', false).text('Update SEO Details');
                            if (res && res.success) {
                                msuNotify('Saved ✓');
                                // sync returned values into model (in case WP made changes)
                                if (res.data) {
                                    model.set({
                                        title: res.data.title || model.get('title'),
                                        alt: res.data.alt || model.get('alt'),
                                        caption: res.data.caption || model.get('caption'),
                                        description: res.data.description || model.get('description')
                                    });
                                }
                            } else {
                                var msg = (res && res.data && res.data.message) ? res.data.message : 'Save failed';
                                msuNotify(msg);
                                console.error('MSU save error', res);
                            }
                        })
                        .fail(function(xhr, status, err){
                            $btn.prop('disabled', false).text('Update SEO Details');
                            msuNotify('Request failed: ' + (xhr.status || status));
                            console.error('MSU AJAX failure', xhr, status, err);
                        });
                });

                // Append to sensible locations in modal
                var $target = view.$el.find('.details, .attachment-info, .attachment-actions');
                if ($target.length) {
                    $target.first().append($btn);
                } else {
                    view.$el.append($btn);
                }
            }

            // Attach to multiple modal view variants (robust)
            var targets = [
                wp.media.view.Attachment.Details,
                (wp.media.view.Attachment.Details && wp.media.view.Attachment.Details.TwoColumn) ? wp.media.view.Attachment.Details.TwoColumn : null,
                wp.media.view.Attachment.Details.Sidebar
            ];

            targets.forEach(function(ViewType){
                if (!ViewType || !ViewType.prototype) return;
                var orig = ViewType.prototype.render;
                ViewType.prototype.render = function(){
                    var result = orig.apply(this, arguments);
                    injectButton(this);
                    return result;
                };
            });

        })(jQuery);
        </script>
        <?php
    }, 20 ); // footer scripts
});

/**
 * AJAX handler: persist attachment fields to DB
 */
add_action( 'wp_ajax_msu_save_attachment', function() {
    // nonce check
    if ( ! isset( $_POST['_ajax_nonce'] ) || ! wp_verify_nonce( $_POST['_ajax_nonce'], 'msu-save-nonce' ) ) {
        wp_send_json_error( array( 'message' => 'Invalid nonce' ), 400 );
    }

    $attachment_id = isset( $_POST['attachment_id'] ) ? intval( $_POST['attachment_id'] ) : 0;
    if ( ! $attachment_id ) {
        wp_send_json_error( array( 'message' => 'No attachment ID' ), 400 );
    }

    // capability check: current user must be able to edit the attachment
    if ( ! current_user_can( 'edit_post', $attachment_id ) ) {
        wp_send_json_error( array( 'message' => 'Insufficient permissions' ), 403 );
    }

    // Sanitize inputs
    $title       = isset( $_POST['title'] ) ? wp_kses_post( wp_unslash( $_POST['title'] ) ) : '';
    $alt         = isset( $_POST['alt'] ) ? sanitize_text_field( wp_unslash( $_POST['alt'] ) ) : '';
    $caption     = isset( $_POST['caption'] ) ? wp_kses_post( wp_unslash( $_POST['caption'] ) ) : '';
    $description = isset( $_POST['description'] ) ? wp_kses_post( wp_unslash( $_POST['description'] ) ) : '';

    // Update post fields: post_title, post_excerpt (caption), post_content (description)
    $update = array(
        'ID'           => $attachment_id,
        'post_title'   => $title,
        'post_excerpt' => $caption,
        'post_content' => $description,
    );

    $result = wp_update_post( $update, true );

    if ( is_wp_error( $result ) ) {
        wp_send_json_error( array( 'message' => 'Could not update attachment' ), 500 );
    }

    // Update alt meta
    update_post_meta( $attachment_id, '_wp_attachment_image_alt', $alt );

    // Return saved values (sanitized)
    $saved = array(
        'title'       => get_the_title( $attachment_id ),
        'alt'         => get_post_meta( $attachment_id, '_wp_attachment_image_alt', true ),
        'caption'     => wp_get_attachment_caption( $attachment_id ),
        'description' => get_post_field( 'post_content', $attachment_id ),
    );

    wp_send_json_success( $saved );
} );