diff --git a/.documentation/addon description/de/description.txt b/.documentation/addon description/de/description.txt
index 6cee6a2..bbb31d4 100644
--- a/.documentation/addon description/de/description.txt
+++ b/.documentation/addon description/de/description.txt
@@ -1,5 +1,8 @@
Dieses Add-on ermöglicht es Nutzern, Webseiten davon abzuhalten, sie über Javascript APIs zu identifizieren. Nutzer können auswählen, ob die APIs komplett auf bestimmten oder allen Seiten blockiert werden (dies wird die Funktionalität einiger Seiten beeinträchtigen) oder bei den identifikationsfreundlichen Auslese-Funktionen falsche Werte vorzutäuschen.
+WICHTIG: Sie sollten nur ein Addon/eine Einstellung aktiv haben, die eine API beschützt. Ansonsten können Sie massive Performanceprobleme bekommen. (Z.B. EclipsedMoon für Palemoon hat 'canvas.poison', was bekanntermaßen Probleme verursacht: https://github.com/kkapsner/CanvasBlocker/issues/253#issuecomment-459499290)
+privacy.resistFingerprinting kann aber problemlos aktiviert werden.
+
Nähere Informationen zum Fingerprinting können Sie finden auf:
- <canvas>: http://www.browserleaks.com/canvas
diff --git a/.documentation/addon description/en/description.txt b/.documentation/addon description/en/description.txt
index 7b97be5..0866ceb 100644
--- a/.documentation/addon description/en/description.txt
+++ b/.documentation/addon description/en/description.txt
@@ -1,5 +1,8 @@
This add-on allows users to prevent websites from using the some Javascript APIs to fingerprint them. Users can choose to block the APIs entirely on some or all websites (which may break some websites) or fake its fingerprinting-friendly readout API.
+IMPORTANT: you should only have ONE addon/setting set that protects an API. Otherwise you could face massive performance issues. (E.g. EclipsedMoon for Palemoon has 'canvas.poison' which is known to cause issues: https://github.com/kkapsner/CanvasBlocker/issues/253#issuecomment-459499290)
+But setting privacy.resistFingerprinting to true is fine.
+
More information on fingerprinting can be found at:
- <canvas>: http://www.browserleaks.com/canvas
diff --git a/README.md b/README.md
index d2009e0..5f53071 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,8 @@
This add-on allows users to prevent websites from using the some Javascript APIs to fingerprint them. Users can choose to block the APIs entirely on some or all websites (which may break some websites) or just block or fake its fingerprinting-friendly readout API.
+**IMPORTANT**: you should only have ONE addon/setting set that protects an API. Otherwise you could face massive performance issues. (E.g. EclipsedMoon for Palemoon has 'canvas.poison' which is known to cause issues: https://github.com/kkapsner/CanvasBlocker/issues/253#issuecomment-459499290)
+But setting privacy.resistFingerprinting to true is fine.
+
More information on fingerprinting can be found at:
* <canvas>: http://www.browserleaks.com/canvas
* audio: