diff --git a/plugins/koinsight.koplugin/call_api.lua b/plugins/koinsight.koplugin/call_api.lua
index eae089a..76d675f 100644
--- a/plugins/koinsight.koplugin/call_api.lua
+++ b/plugins/koinsight.koplugin/call_api.lua
@@ -6,7 +6,7 @@ local http = require("socket.http")
 local UIManager = require("ui/uimanager")
 local JSON = require("json")
 local InfoMessage = require("ui/widget/infomessage")
-local _ = require("gettext")
+local _ = require("koinsight_l10n")
 
 function response_not_valid(content)
   logger.err("[KoInsight] callApi: response was not valid JSON", content)
@@ -65,7 +65,7 @@ return function(method, url, headers, body, filepath, quiet)
     if not quiet then
       logger.err("[KoInsight] callApi: HTTP error", status or code, resp_headers, result)
       UIManager:show(InfoMessage:new({
-        text = _("Server error" .. (result and ": " .. result["error"] or "")),
+        text = _("Server error") .. (result and ": " .. result["error"] or ""),
       }))
     end
 
diff --git a/plugins/koinsight.koplugin/koinsight_l10n.lua b/plugins/koinsight.koplugin/koinsight_l10n.lua
new file mode 100644
index 0000000..7d52e85
--- /dev/null
+++ b/plugins/koinsight.koplugin/koinsight_l10n.lua
@@ -0,0 +1,68 @@
+-- Plugin-local translations for KoInsight.
+-- KOReader's gettext catalog only covers core strings, so plugin strings are
+-- looked up here first and fall back to KOReader's gettext (i.e. English).
+local gettext = require("gettext")
+
+local translations = {
+  sk = {
+    ["About KoInsight"] = "O doplnku KoInsight",
+    ["Aggressive suspend sync disabled"] = "Agresívna synchronizácia pri uspaní vypnutá",
+    ["Aggressive suspend sync enabled"] = "Agresívna synchronizácia pri uspaní zapnutá",
+    ["Aggressive sync on suspend (auto Wi-Fi)"] = "Agresívna synchronizácia pri uspaní (automatické Wi-Fi)",
+    ["Apply"] = "Použiť",
+    ["Cancel"] = "Zrušiť",
+    ["Data upload failed."] = "Odoslanie údajov zlyhalo.",
+    ["Data uploaded."] = "Údaje boli odoslané.",
+    ["Enter the location of your KoInsight server"] = "Zadajte adresu vášho servera KoInsight",
+    ["Error during auto sync: "] = "Chyba pri automatickej synchronizácii: ",
+    ["Error toggling aggressive sync setting"] = "Chyba pri prepínaní agresívnej synchronizácie",
+    ["Error toggling sync setting"] = "Chyba pri prepínaní nastavenia synchronizácie",
+    ["Error:"] = "Chyba:",
+    ["Info"] = "Informácie",
+    ["KoInsight is a sync plugin for KoInsight instances.\n\nPlugin version: %s\n\nSee https://github.com/GeorgeSG/koinsight."] = "KoInsight je synchronizačný doplnok pre inštancie KoInsight.\n\nVerzia doplnku: %s\n\nViac na https://github.com/GeorgeSG/koinsight.",
+    ["KoInsight server URL is not configured."] = "URL servera KoInsight nie je nastavená.",
+    ["KoInsight settings saved."] = "Nastavenia KoInsight boli uložené.",
+    ["KoInsight settings"] = "Nastavenia KoInsight",
+    ["KoInsight: Sync all books"] = "KoInsight: Synchronizovať všetky knihy",
+    ["No books with annotations found in reading history."] = "V histórii čítania sa nenašli žiadne knihy s poznámkami.",
+    ["Please configure the server URL first."] = "Najprv nastavte URL servera.",
+    ["Please enter a server URL."] = "Zadajte URL servera.",
+    ["Server URL:"] = "URL servera:",
+    ["Server error"] = "Chyba servera",
+    ["Server response is not valid."] = "Odpoveď servera nie je platná.",
+    ["Set server URL"] = "Nastaviť URL servera",
+    ["Set suspend connect timeout…"] = "Nastaviť časový limit pripojenia pri uspaní…",
+    ["Starting sync..\nScanning reading history for books with annotations."] = "Spúšťam synchronizáciu…\nPrehľadávam históriu čítania a hľadám knihy s poznámkami.",
+    ["Success:"] = "Úspech:",
+    ["Suspend connect timeout (seconds)"] = "Časový limit pripojenia pri uspaní (sekundy)",
+    ["Sync complete!\n%d/%d books synced successfully\n%d failed"] = "Synchronizácia dokončená!\n%d/%d kníh úspešne synchronizovaných\nNeúspešné: %d",
+    ["Sync failed: "] = "Synchronizácia zlyhala: ",
+    ["Sync on suspend disabled"] = "Synchronizácia pri uspaní vypnutá",
+    ["Sync on suspend enabled"] = "Synchronizácia pri uspaní zapnutá",
+    ["Sync on suspend"] = "Synchronizovať pri uspaní",
+    ["Synchronize data"] = "Synchronizovať údaje",
+    ["Syncing: %d/%d books\n%d annotations for current book"] = "Synchronizácia: %d/%d kníh\n%d poznámok v aktuálnej knihe",
+    ["The server URL must start with 'http://' or 'https://'.\n\n"] = "URL servera musí začínať na 'http://' alebo 'https://'.\n\n",
+    ["Timeout (3..60):"] = "Limit (3..60):",
+    ["Timeout saved."] = "Časový limit bol uložený.",
+    ["Unable to register device."] = "Zariadenie sa nepodarilo zaregistrovať.",
+    ["http://example.com:port"] = "http://priklad.sk:port",
+  },
+}
+
+local function currentLanguage()
+  local lang = gettext.current_lang
+  if (not lang or lang == "C") and G_reader_settings then
+    lang = G_reader_settings:readSetting("language")
+  end
+  if not lang then
+    return nil
+  end
+  -- "sk_SK" / "sk-SK" -> "sk"
+  return lang:match("^(%a+)")
+end
+
+return function(msgid)
+  local catalog = translations[currentLanguage()]
+  return (catalog and catalog[msgid]) or gettext(msgid)
+end
diff --git a/plugins/koinsight.koplugin/main.lua b/plugins/koinsight.koplugin/main.lua
index 1f3c33c..ad93fa2 100644
--- a/plugins/koinsight.koplugin/main.lua
+++ b/plugins/koinsight.koplugin/main.lua
@@ -1,4 +1,4 @@
-local _ = require("gettext")
+local _ = require("koinsight_l10n")
 local Dispatcher = require("dispatcher") -- luacheck:ignore
 local InfoMessage = require("ui/widget/infomessage")
 local logger = require("logger")
@@ -89,9 +89,10 @@ function koinsight:addToMainMenu(menu_items)
         callback = function()
           local const = require("./const")
           UIManager:show(InfoMessage:new({
-            text = "KoInsight is a sync plugin for KoInsight instances.\n\nPlugin version: "
-              .. const.VERSION
-              .. "\n\nSee https://github.com/GeorgeSG/koinsight.",
+            text = string.format(
+              _("KoInsight is a sync plugin for KoInsight instances.\n\nPlugin version: %s\n\nSee https://github.com/GeorgeSG/koinsight."),
+              const.VERSION
+            ),
           }))
         end,
       },
@@ -171,7 +172,7 @@ function koinsight:performFullSync()
     if not ok then
       UIManager:close(progress_info)
       logger.err("[KoInsight] Full sync failed: " .. tostring(err))
-      UIManager:show(InfoMessage:new({ text = _("Sync failed: " .. tostring(err)), timeout = 5 }))
+      UIManager:show(InfoMessage:new({ text = _("Sync failed: ") .. tostring(err), timeout = 5 }))
     end
   end)
 end
@@ -244,10 +245,10 @@ function koinsight:performSyncOnSuspend()
   end)
 
   if not success then
-    message = "Error during auto sync: " .. tostring(error_msg)
+    local message = "Error during auto sync: " .. tostring(error_msg)
     logger.err("[KoInsight] " .. message)
     UIManager:show(InfoMessage:new({
-      text = _(message),
+      text = _("Error during auto sync: ") .. tostring(error_msg),
     }))
   else
     logger.info("[KoInsight] Suspend sync completed successfully")
diff --git a/plugins/koinsight.koplugin/settings.lua b/plugins/koinsight.koplugin/settings.lua
index 5c1febd..8444f67 100644
--- a/plugins/koinsight.koplugin/settings.lua
+++ b/plugins/koinsight.koplugin/settings.lua
@@ -1,4 +1,4 @@
-local _ = require("gettext")
+local _ = require("koinsight_l10n")
 local BD = require("ui/bidi")
 local DataStorage = require("datastorage")
 local InfoMessage = require("ui/widget/infomessage")
diff --git a/plugins/koinsight.koplugin/upload.lua b/plugins/koinsight.koplugin/upload.lua
index 912bc95..8091886 100644
--- a/plugins/koinsight.koplugin/upload.lua
+++ b/plugins/koinsight.koplugin/upload.lua
@@ -1,4 +1,4 @@
-local _ = require("gettext")
+local _ = require("koinsight_l10n")
 local callApi = require("call_api")
 local InfoMessage = require("ui/widget/infomessage")
 local JSON = require("json")
@@ -30,7 +30,7 @@ function render_response_message(response, prefix, default_text)
   end
 
   UIManager:show(InfoMessage:new({
-    text = _(text),
+    text = text,
   }))
 end
 
@@ -46,7 +46,7 @@ function send_device_data(server_url, silent)
   local ok, response = callApi("POST", url, get_headers(body), body)
 
   if ok ~= true and not silent then
-    render_response_message(response, "Error:", "Unable to register device.")
+    render_response_message(response, _("Error:"), _("Unable to register device."))
   end
 end
 
@@ -78,9 +78,9 @@ function send_statistics_data(server_url, silent)
 
   if not silent then
     if ok then
-      render_response_message(response, "Success:", "Data uploaded.")
+      render_response_message(response, _("Success:"), _("Data uploaded."))
     else
-      render_response_message(response, "Error:", "Data upload failed.")
+      render_response_message(response, _("Error:"), _("Data upload failed."))
     end
   end
 end