diff --git a/README.md b/README.md
index 198c74c..1d5a296 100644
--- a/README.md
+++ b/README.md
@@ -151,12 +151,13 @@ func (Post) MorphName() string             { return `Golem15\Journal\Models\Post
 
 ### Blog Editor
 
-`assets/src/blogeditor` is the Blog Editor admin element, the custom element `golem15-journal-blogeditor` (`BlogEditorElement`). It is a WYSIWYG HTML editor on TipTap (ProseMirror, MIT) with a Source tab that shows and edits the exact HTML string. The toolbar offers paragraphs and headings 2 to 4, bold, italic, bullet and ordered lists, links, blockquotes, tables, images, YouTube embeds, a raw HTML block, undo and redo. Labels follow the `ui-locale` attribute (`en`, `pl`).
+`assets/src/blogeditor` is the Blog Editor admin element, the custom element `golem15-journal-blogeditor` (`BlogEditorElement`). It is a WYSIWYG HTML editor on TipTap (ProseMirror, MIT) with a Source tab that shows and edits the exact HTML string. The toolbar offers paragraphs and headings 2 to 4, bold, italic, bullet and ordered lists, links, blockquotes, tables, images, YouTube embeds, a raw HTML block, undo and redo, plus a Preview toggle. Labels follow the `ui-locale` attribute (`en`, `pl`).
 
 The element follows the admin field type element contract: the `value` property holds the HTML string; the attributes are `field-name`, `record-id`, `locale`, `ui-locale`, `options`, `disabled` and `invalid`; a bubbling `summer-change` event with `detail.value` fires on user edits only. It styles itself only through the admin `--c-*` variables, in `blogeditor.css` under its tag (TipTap's injected stylesheet is off), and never receives or sends credentials.
 
 - **Untouched values.** The element returns the exact string it was given until the user edits; an untouched imported post is saved byte for byte. Setting `value` to the string it currently returns is a no-op. After an edit, top-level blocks that are still equal to the loaded ones keep their original bytes, so editing one paragraph changes only that paragraph. Markup the schema does not model (`footer`, `section`, `aside`, `header`, `nav`, `details`, `style`, `div` and similar blocks, and a `figure` that is not an image with an optional caption) becomes a raw HTML card that shows its source as text and is written back verbatim. Unmodelled attributes on paragraphs, headings, lists, blockquotes, tables, cells, images and links, and `span` elements with attributes, survive an edit; event handler attributes (`on*`) are never kept.
 - **Embeds.** The embed button takes a YouTube URL (`youtube.com/watch?v=`, `youtu.be/`, `youtube.com/shorts/`, `youtube.com/embed/`) and stores exactly `<figure data-embed="youtube" data-id="ID"></figure>`, where `ID` matches `^[A-Za-z0-9_-]{11}$`. The admin shows a card and never an iframe; the site layer expands the placeholder. Another provider is one entry in `EMBED_PROVIDERS` (`embed.ts`) and one in the layer.
+- **Preview.** The Preview button (`Podgląd` for `ui-locale` `pl`) is off by default, belongs to each element on its own and shows its state through `aria-pressed`. It splits the editor 50/50; when the element is narrower than about 720px, the pane wraps below the editor. The pane renders the current value from the WYSIWYG or Source tab 300 ms (`PREVIEW_DEBOUNCE_MS` in `preview.ts`) after the last change, and each update reloads the frame. The frame is an `<iframe srcdoc>` with an empty `sandbox` attribute, so no scripts run and its origin is opaque. It has `referrerpolicy="no-referrer"` and a Content-Security-Policy meta (`PREVIEW_CSP`) that allows only inline styles and images. The preview copy leaves out `script`, `iframe`, `frame`, `frameset`, `object`, `embed`, `meta`, `base` and `link` elements and event handler attributes. YouTube placeholders show as thumbnail cards loaded from img.youtube.com, never as a player; these and the post's own images are the only network traffic the pane makes. The styling is post-body typography, with the `--c-*` values read from the element at render time or neutral defaults. Previewing never fires `summer-change` and never changes the value, so an untouched post is still saved byte for byte.
 - **Links.** The editor creates and keeps links only to `http`, `https`, `mailto` and relative URLs (`isPolicyUrl` in `extensions.ts`), the schemes both sanitizer policies keep; the scheme is read after removing control characters and spaces. A created link has `href` only; stored links keep their own `target` and `rel`, which the server strips on an edited save.
 - **Images.** An image chosen with the file picker (JPEG, PNG, GIF, WebP) or dropped on the editor is handed to the admin page as a bubbling `summer-upload` event with `detail {id, file}`. The admin uploads it with its own session and answers on the element with `summer-upload-result` `{id, url}` or `{id, error}`. On a URL the editor asks for the alt text (required) and an optional caption and inserts `<img src alt>`, or `<figure>` with `<img>` and `<figcaption>` when a caption is given. An error, or no answer within 60 seconds, is shown in the status line and nothing is inserted.
 - **Sanitizing.** The element never sanitizes. Every admin save goes through `classes.SanitizeHTMLReport`, which strips what the policy does not allow and reports it; the policy keeps all of the editor's own output.
@@ -183,6 +184,8 @@ The plugin registers two admin form field types (`journal.Plugin.FormFieldTypes`
 | `blogeditor` | One HTML string in a host column (category content). | `uploadFolder` |
 | `mlblogeditor` | One HTML string per content locale, stored like `mlmarkdown`: the default locale in the host column, the others as translations (post content). | `htmlColumn`, `uploadFolder` |
 
+Both types show the element's Preview pane, and previewing never changes what a save stores.
+
 `htmlColumn` names the translatable attribute that holds the rendered HTML of a markdown value (`content_html` for posts). `uploadFolder` is the folder under `/journal/` that editor images are stored in (`posts`, `categories`; `editor` when unset); it follows the public upload route's folder rule (at most 100 letters, digits, `_`, `-` or `/`, no `..`) and is checked at boot.
 
 ```yaml