diff --git a/lib/builtin_query_functions.ts b/lib/builtin_query_functions.ts
index fa462142..b82bba90 100644
--- a/lib/builtin_query_functions.ts
+++ b/lib/builtin_query_functions.ts
@@ -2,8 +2,15 @@ import type { FunctionMap } from "../plug-api/types.ts";
 import { niceDate, niceTime } from "./dates.ts";
 
 export const builtinFunctions: FunctionMap = {
-  today() {
-    return niceDate(new Date());
+  // String functions
+  contains(str: unknown, substr: unknown) {
+    if (typeof str !== "string") {
+      throw new Error("contains(): str is not a string");
+    }
+    if (typeof substr !== "string") {
+      throw new Error("contains(): substr is not a string");
+    }
+    return str.includes(substr);
   },
   replace(
     str: unknown,
@@ -72,6 +79,9 @@ export const builtinFunctions: FunctionMap = {
   escapeDirective: (directiveText: unknown) => {
     return `{{${directiveText}}}`;
   },
+  today() {
+    return niceDate(new Date());
+  },
   time: () => niceTime(new Date()),
   tomorrow: () => {
     const tomorrow = new Date();
diff --git a/website/CHANGELOG.md b/website/CHANGELOG.md
index bf268b2f..1e227f8a 100644
--- a/website/CHANGELOG.md
+++ b/website/CHANGELOG.md
@@ -6,7 +6,7 @@ release.
 ## Edge
 _These features are not yet properly released, you need to use [the edge builds](https://community.silverbullet.md/t/living-on-the-edge-builds/27) to try them._
 
-* Nothing yet since 0.7.4, be patient!
+* Added [[Functions#contains(str, substr)]] function
 
 ## 0.7.5
 * [[Plugs/Share]] using the {[Share: Page Or Selection]} command (bound to Ctrl-s/Cmd-s by default): allowing you to quickly share the current page (or selection) to the clipboard as:
diff --git a/website/Functions.md b/website/Functions.md
index c21c2d10..7b0ef7fa 100644
--- a/website/Functions.md
+++ b/website/Functions.md
@@ -46,6 +46,9 @@ Replace text in a string. `match` can either be a literal string or a regular ex
 
 This function supports an infinite number of replacements, so you can keep adding more, e.g. `replace(str, match1, replacement1, match2, replacement2, match3, replacement3)`
 
+## contains(str, substr)
+Returns whether `str` contains `substr` as a substring.
+
 ## json(obj)
 Convert the argument to a JSON string (for debugging purposes).