A browser extension that overlays a floating panel on poe.ninja and helps you make profitable decisions at several endgame crafting mechanics in Path of Exile:
- Labyrinth Divine Font — which transfigured gems to hunt
- Harvest crafting — whether to swap Catalysts, Essences, Delirium Orbs, or Astrolabes for profit
- Forbidden Jewels — average market price of Forbidden Flame and Forbidden Flesh variants in divines
The Divine Font offers two ways to transfigure a gem:
- Color Roll — insert any gem of a colour and receive a random transfigured gem from that colour's entire pool (equal chance for each gem in the pool).
- Specific Roll — insert a specific base gem and receive one of that gem's transfigured variants at random (equal chance per variant).
GemCheck calculates the expected value (EV) and hit probabilities for both modes using live poe.ninja pricing so you can make informed decisions before running the lab.
The Harvest crafting bench lets you swap a currency item (Catalyst, Essence, or Delirium Orb) for a random item of the same type. The swap costs Crystallised Lifeforce.
GemCheck shows:
- Pool EV — the weighted average sell price across all possible outcomes
- Craft threshold — pool EV minus craft cost; items priced below this are worth sacrificing for a reroll
- ▲ keep / ▼ craft — per-item indicators showing whether to hold or swap
Drop probabilities for Catalysts and Delirium Orbs are based on ~2000 observed swaps by lifewithoutpants_ (YouTube).
- Color Roll Bingo — for each colour (Red / Green / Blue) shows the top target gems with pool EV, hit probability per gem, and current sell price.
- Best Specific Gems — a combined cross-colour ranking of all base gems sorted by EV, with every variant's probability and sell price listed.
- Configurable Top N — choose how many gems to show per section (3 / 5 / 8).
- Level/quality filter — switch between lvl 1 q 0%, lvl 1 q 20%, lvl 20 q 0%, and lvl 20 q 20% to compare prices across gem states.
- Catalysts — weighted EV with observed drop probabilities; excludes Dextral, Sinistral, and Tainted Catalysts (different mechanic).
- Essences — EV for Deafening Essence swaps.
- Delirium Orbs — weighted EV with observed drop probabilities.
- Astrolabes — EV for Astrolabe swaps (400 Primal Lifeforce per swap).
- ▲ keep / ▼ craft indicators — tells you at a glance which items are worth sacrificing.
- Avg price in divines for Forbidden Flame and Forbidden Flesh across all passive variants.
- Two rows: all variants, and excluding 7 hidden ascendancy passives unavailable in-game.
- Columns: avg · σ (standard deviation) · min · max.
- Live pricing — pulls directly from poe.ninja's public API for the current league. Data is cached for 5 minutes; a Refresh button busts the cache.
- League auto-detection — reads the league from the poe.ninja URL automatically.
- Draggable panel — reposition anywhere on screen; minimise or close when not needed.
Prices shown are raw sell prices (cheapest listing on poe.ninja). Craft cost uses live Crystallised Lifeforce prices. Base gem cost and lab fees are not deducted.
Install GemCheck on the Chrome Web Store
Install GemCheck on Firefox Add-ons
Works with any Chromium-based browser: Chrome, Brave, Opera GX, Vivaldi, Edge.
- Go to the Releases page and download
gemcheck.zip. - Unzip it — you'll get a folder with
manifest.json,src/, andassets/. - Open Chrome and go to
chrome://extensions. - Enable Developer mode (top-right toggle).
- Click Load unpacked and select the unzipped folder.
- Navigate to
poe.ninja › Economy › [your league] › Skill Gems— the panel appears automatically.
- Go to the Releases page and download
gemcheck_firefox.zip. - Open Firefox and go to
about:debugging→ This Firefox. - Click Load Temporary Add-on and select the zip directly (no need to unzip).
- Navigate to
poe.ninja › Economy › [your league] › Skill Gems— the panel appears automatically.
Note: Temporary add-ons are removed when Firefox restarts. For a permanent install, the extension would need to be signed via addons.mozilla.org.
The panel appears automatically on the relevant poe.ninja pages.
Divine Font (Skill Gems):
- Go to
poe.ninja › Economy › [your league] › Skill Gems. - Use the Top N selector to control how many gems are shown per colour.
Harvest Swap (Catalysts / Essences / Deli Orbs / Astrolabes):
- Go to
poe.ninja › Economy › [your league] › Currency(Catalysts),Essences,Delirium Orbs, orAstrolabes. - Items marked ▲ are worth holding; items marked ▼ are worth sacrificing for a reroll.
Forbidden Jewels:
- Go to
poe.ninja › Economy › [your league] › Forbidden Jewels. - The panel shows avg, σ, min, max prices in divines for Forbidden Flame and Forbidden Flesh — with and without the 7 hidden ascendancy passives.
General:
- Click Refresh to fetch the latest prices.
- Drag the panel anywhere on screen; click — to minimise or ✕ to close.
- Python 3 (stdlib only, no pip required)
- make (optional, all commands have Python equivalents)
make fetch # pull latest gem data from poewiki
make update # rewrite gem arrays in content.js from fetched JSONs
make pack # build gemcheck.zip ready for the Chrome Web Store
make release # all three in one shot (new league? run this)
make screenshot # generate assets/screenshot_store.png from newest PNG in root
make version # print current version
make clean # remove gemcheck.zipmake screenshot auto-detects the newest brave_*.png or Screenshot*.png in the project root. To use a specific file:
make screenshot SRC=path/to/file.png- Open
chrome://extensions - Enable Developer mode (top-right toggle)
- Click Load unpacked → select this folder
- Make changes to
content.js, then click ↻ inchrome://extensionsto reload
make releaseThis scrapes poewiki for the latest base gem and transfigured gem lists, updates the static arrays in content.js, and rebuilds the zip.
- Gem prices — poe.ninja public API (
/api/data/itemoverview?type=SkillGem) - Gem colour data — poewiki.net/wiki/List_of_skill_gems
- Catalyst / Deli Orb / Astrolabe prices — poe.ninja exchange API (
/api/economy/exchange/current/overview) - Essence prices — poe.ninja item API (
/api/data/itemoverview) - Forbidden Jewel prices — poe.ninja stash API (
/poe1/api/economy/stash/current/item/overview?type=ForbiddenJewel) - Catalyst & Deli Orb drop weights — ~2000 observed swaps by lifewithoutpants_ (YouTube)
GemCheck collects no user data. See PrivacyPolicy.md for full details.