AssesPhoto Keyboard Navigation & Download
A Tampermonkey (or scriptcat) userscript that adds keyboard controls and an original-image download button to the lightbox (presentation mode) on assesphoto.com.
Features
- ← / → arrow keys — navigate to the previous / next image in the lightbox (wraps around at both ends, same as clicking the on-screen arrows)
- Esc — close the lightbox
- D key or ⬇ button — download the currently displayed original image, with content validation so you never save a corrupt file
- A floating download button rendered in the bottom-right corner of the lightbox, positioned to avoid overlapping the thumbnail strip and navigation arrows; it shows ⏳ / ✓ / ⚠ states during and after each download
- Downloaded files are named
<gallery title> - <filename>.jpg, so images from different galleries never collide
Keys are only intercepted while the lightbox is open, and never while focus is in an input field (e.g. the site's search box) — normal page browsing is unaffected.
Installation
- Install Tampermonkey (or Violentmonkey) for your browser.
- Create a new script in the Tampermonkey dashboard (
+ icon).
- Paste the full contents of
assesphoto-keyboard-nav.user.js and save (Ctrl+S).
- Open any gallery page, e.g.
https://www.assesphoto.com/granny-exposing-her-asshole.shtml, click a photo to enter presentation mode, and use the keyboard.
Key Bindings
| Key |
Action |
← |
Previous image |
→ |
Next image |
Esc |
Close lightbox |
D |
Download current image (plain D only — not Ctrl+D/Cmd+D/Alt+D) |
How It Works
The site's lightbox is driven by plain global functions (prevImage(), nextImage(), closeModal()) attached to onclick handlers. The script:
- Listens for
keydown on document in the capture phase, so it runs before any page-level handlers.
- Checks whether the lightbox (
#myModal) is open before acting.
- Calls the site's own navigation functions directly (falling back to clicking the arrow buttons if the functions are ever renamed), which keeps the thumbnail highlighting in sync.
Why GM.xmlHttpRequest + content validation?
The images are served from a separate host (img.assesphoto.com) behind Cloudflare that sends no CORS headers. Both fetch() and the <a download> attribute are therefore useless from the page context — the browser either blocks the request or ignores the download attribute for cross-origin URLs.
The script fetches the image as a Blob via Tampermonkey's GM.xmlHttpRequest (with the corresponding @connect img.assesphoto.com declaration), which bypasses page CORS. Before saving, it validates the blob's magic bytes (JPEG/PNG/GIF/WebP) — if Cloudflare occasionally serves an HTML challenge page instead of the image, the download is aborted and the image opens in a new tab as a fallback, so you never end up with a corrupt .jpg file on disk.
Two further guards against corrupt downloads:
- Modifier keys are ignored:
Ctrl+D / Cmd+D / Alt+D belong to the browser (bookmark dialog) and no longer trigger a download at the same time.
- Key repeat + double-press protection: holding
D or pressing it twice quickly can no longer start two concurrent downloads of the same file, which would race Chrome's .crdownload handling and leave a broken file. A downloading flag gates concurrent requests, and the button shows ⏳ / ✓ / ⚠ states.
Referer requirement & cache pre-warming
Two server-side behaviors shape the download pipeline:
- Hotlink protection: the image host returns
404 Not Found (13 bytes of plain text) to any request without a Referer: https://www.assesphoto.com/ header. GM.xmlHttpRequest calls fired from the extension background don't carry the page's Referer automatically, so the script sets it explicitly. This matters because that tiny 404 text body was the source of the "downloaded file is invalid" bug in earlier versions (see below).
- Cloudflare request fingerprinting: native browser image loads (
Sec-Fetch-Dest: image) always pass, while XHR-fingerprinted requests can be challenged. Before fetching, the script pre-loads the URL through a plain <img> element in the page, which both verifies the URL decodes as a real image and writes the response into the browser's HTTP cache and Cloudflare's edge cache. The subsequent GM.xmlHttpRequest for the exact same URL hits the warm cache and receives the just-validated bytes. If the image is already displayed and fully loaded in the lightbox (the common case), even the pre-warm step is skipped. Measured on the live site: first load ≈ 1.2 s, immediately-repeated load of the same URL = 0 ms (pure cache hit).
The full download pipeline, in order:
<img> pre-warm (skipped if the displayed image is already complete) — fails only if the URL itself is deadGM.xmlHttpRequest blob fetch (with Referer header) + magic-byte validation, up to 3 attempts (re-warming between attempts, escalating backoff)- New tab — only if everything above fails; the browser navigation carries the page's Referer automatically, so the image always loads there
GM_download is deliberately not used anywhere: it goes through chrome.downloads, which sends no Referer — on this host that guarantees the 404 text body gets saved as a .jpg. Every byte written to disk passes magic-byte validation first.
Site Quirk: Duplicated Images
The gallery's images array lists every image twice (and the thumbnail strip renders matching duplicate pairs), so the array has 20 entries for 10 actual photos. This means a single keypress sometimes lands on the "same" photo twice before advancing to a new one — this mirrors the on-screen arrows exactly, since the script reuses the site's own navigation logic.
Troubleshooting
"The download fires, but the saved file is invalid." (Fixed in v1.5.0)
Two stacked causes: the image host enforces hotlink protection and returns a 13-byte 404 Not Found text body to Referer-less requests (which GM.xmlHttpRequest was sending after the header was removed in v1.2.0), and the v1.4.0 GM_download fallback saved whatever arrived without validation — including that 404 text — as a .jpg. The Referer header is now sent explicitly, and the unvalidatable GM_download fallback was removed entirely; nothing reaches disk without passing the magic-byte check.
"Sometimes clicking download just opens a new tab instead of downloading." (Fixed in v1.4.0)
The new tab was the fallback path: the XHR-fingerprinted fetch was being consistently challenged by Cloudflare for certain requests, so even retries failed. The script now pre-warms the URL through a plain <img> load (which Cloudflare never challenges) before fetching, so the download request hits a validated cache entry instead of the challengeable cold path. See Referer requirement & cache pre-warming.
"Sometimes the downloaded file is not a valid image." (Fixed in v1.2.0)
This was traced to three separate causes, all now handled:
- Browser-shortcut collision — pressing
Ctrl+D used to trigger a download and open the browser's bookmark dialog at the same time; the focus steal could interrupt the download mid-write. Downloads now only fire on a plain D press.
- Concurrent same-name downloads — key auto-repeat (holding
D) or double-pressing started parallel downloads of the same file, racing Chrome's .crdownload handling and leaving a broken file. A downloading flag now serializes downloads.
- Cloudflare HTML responses — the image host occasionally serves an HTML challenge page instead of the image. Every response is now magic-byte-validated before saving; invalid responses are retried, then fall back to opening the image in a new tab instead of writing a corrupt
.jpg.
If a download still fails, check the browser console for [kb-nav] warnings, which log each failed attempt with the response status and content type.
Compatibility
Tested with Tampermonkey on Chrome and Edge. The script uses GM.xmlHttpRequest, which is supported by Violentmonkey and Greasemonkey 4 (GM.xmlHttpRequest) as well.
Edge note (v1.6.0)
On Edge, Tampermonkey tends to run userscripts in an isolated sandbox where the page's global functions (prevImage / nextImage / closeModal) are not visible on the sandboxed window, so the old single-path call silently failed — and since the keydown handler then did nothing, the arrow keys fell through to their browser default: scrolling the thumbnail strip's horizontal scrollbar, which looked like "the scrollbar steals the keys". Navigation now goes through a three-level fallback (unsafeWindow → window → clicking the page's real .nav-button DOM buttons, each guarded by try/catch), the keydown listener is attached in the capture phase on both window and document, and arrow keys are always preventDefault()-ed so they can never scroll the thumbnail strip. A startup self-check line ([kb-nav] v1.6.0 就绪 …) is logged to the console showing which level is available, to make future diagnosis a one-glance task.
Changelog
- 1.6.0 — Edge compatibility: three-level navigation fallback (
unsafeWindow → window → real DOM button click) with per-level try/catch, capture-phase keydown on both window and document, arrows always preventDefault()-ed (stops the thumbnail-strip scrollbar from consuming the keys when navigation fails), and a startup self-check log line. Fixes "works in Chrome, arrow keys only scroll the scrollbar in Edge".
- 1.5.0 — Root-cause fix for corrupt downloads: explicit
Referer header on the blob fetch (the host's hotlink protection 404s Referer-less requests with a text body), and removal of the GM_download fallback, which saved that unvalidated 404 text as a .jpg. Every byte written to disk now passes magic-byte validation.
- 1.4.0 — Cache pre-warming: the URL is validated and cached via a native
<img> load before the blob fetch, so Cloudflare's challengeable cold path is bypassed entirely; GM_download added as an intermediate fallback before the new-tab escape hatch.
- 1.3.0 — Automatic retry for Cloudflare-challenged responses: 3 attempts with escalating backoff, native-style
Accept header, 15 s request timeout. Fixes intermittent "download degrades to new-tab fallback".
- 1.2.0 — Download hardening: magic-byte content validation (JPEG/PNG/GIF/WebP),
GM.xmlHttpRequest blob fetch replaces GM_download, modifier-key (Ctrl/Cmd/Alt+D) and key-repeat guards, concurrent-download lock, button progress states, filename trailing-dot/space sanitization. Fixes intermittent corrupt downloads.
- 1.1.0 — Added original-image download:
D key and floating ⬇ button, GM_download-based, <gallery title> - <filename> naming.
- 1.0.0 — Initial release:
← / → lightbox navigation, Esc to close.
License
MIT
s
