diff --git a/src/chooser.ts b/src/chooser.ts
index de65aaf9..b04870a5 100644
--- a/src/chooser.ts
+++ b/src/chooser.ts
@@ -295,13 +295,13 @@ export class Chooser extends LitElement {
                   type="text"
                   name="filename"
                   id="filename"
-                  pattern="((file|http|https|ipfs|s3)://.*.(warc|warc.gz|zip|wacz|har|json)([?#].*)?)|(googledrive://.+)|(ssb://.+)"
+                  pattern="((file|http|https|ipfs|s3)://.*.(warc|warc.gz|zip|wacz|har|json|cdx|cdxj)([?#].*)?)|(googledrive://.+)|(ssb://.+)"
                   .value="${this.fileDisplayName}"
                   @input="${this.onInput}"
                   autocomplete="off"
                   placeholder="${this.newFullImport
                     ? "Click 'Choose File' to select a local archive to import"
-                    : "Enter a URL or click 'Choose File' to select a WARC, WACZ, or HAR file"}"
+                    : "Enter a URL or click 'Choose File' to select a WARC, WACZ, CDX, or HAR file"}"
                 />
               </p>
               <div class="control">