diff --git a/src/js/devtools.js b/src/js/devtools.js
index 629cd36b1..92cd07894 100644
--- a/src/js/devtools.js
+++ b/src/js/devtools.js
@@ -21,6 +21,7 @@
 
 /* global CodeMirror, uBlockDashboard */
 
+import * as s14e from './s14e-serializer.js';
 import { dom, qs$ } from './dom.js';
 
 /******************************************************************************/
@@ -79,6 +80,100 @@ function log(text) {
     cmEditor.replaceRange(text.trim() + '\n\n', { line: 0, ch: 0 });
 }
 
+/******************************************************************************/
+
+function toDNRText(raw) {
+    const result = s14e.deserialize(raw);
+    if ( typeof result === 'string' ) { return result; }
+    const { network } = result;
+    const replacer = (k, v) => {
+        if ( k.startsWith('__') ) { return; }
+        if ( Array.isArray(v) ) {
+            return v.sort();
+        }
+        if ( v instanceof Object ) {
+            const sorted = {};
+            for ( const kk of Object.keys(v).sort() ) {
+                sorted[kk] = v[kk];
+            }
+            return sorted;
+        }
+        return v;
+    };
+    const isUnsupported = rule =>
+        rule._error !== undefined;
+    const isRegex = rule =>
+        rule.condition !== undefined &&
+        rule.condition.regexFilter !== undefined;
+    const isRedirect = rule =>
+        rule.action !== undefined &&
+        rule.action.type === 'redirect' &&
+        rule.action.redirect.extensionPath !== undefined;
+    const isCsp = rule =>
+        rule.action !== undefined &&
+        rule.action.type === 'modifyHeaders';
+    const isRemoveparam = rule =>
+        rule.action !== undefined &&
+        rule.action.type === 'redirect' &&
+        rule.action.redirect.transform !== undefined;
+    const { ruleset } = network;
+    const good = ruleset.filter(rule =>
+        isUnsupported(rule) === false &&
+        isRegex(rule) === false &&
+        isRedirect(rule) === false &&
+        isCsp(rule) === false &&
+        isRemoveparam(rule) === false
+    );
+    const unsupported = ruleset.filter(rule =>
+        isUnsupported(rule)
+    );
+    const regexes = ruleset.filter(rule =>
+        isUnsupported(rule) === false &&
+        isRegex(rule) &&
+        isRedirect(rule) === false &&
+        isCsp(rule) === false &&
+        isRemoveparam(rule) === false
+    );
+    const redirects = ruleset.filter(rule =>
+        isUnsupported(rule) === false &&
+        isRedirect(rule)
+    );
+    const headers = ruleset.filter(rule =>
+        isUnsupported(rule) === false &&
+        isCsp(rule)
+    );
+    const removeparams = ruleset.filter(rule =>
+        isUnsupported(rule) === false &&
+        isRemoveparam(rule)
+    );
+    const out = [
+        `dnrRulesetFromRawLists(${JSON.stringify(result.listNames, null, 2)})`,
+        `Run time: ${result.runtime} ms`,
+        `Filters count: ${network.filterCount}`,
+        `Accepted filter count: ${network.acceptedFilterCount}`,
+        `Rejected filter count: ${network.rejectedFilterCount}`,
+        `Un-DNR-able filter count: ${unsupported.length}`,
+        `Resulting DNR rule count: ${ruleset.length}`,
+    ];
+    out.push(`+ Good filters (${good.length}): ${JSON.stringify(good, replacer, 2)}`);
+    out.push(`+ Regex-based filters (${regexes.length}): ${JSON.stringify(regexes, replacer, 2)}`);
+    out.push(`+ 'redirect=' filters (${redirects.length}): ${JSON.stringify(redirects, replacer, 2)}`);
+    out.push(`+ 'csp=' filters (${headers.length}): ${JSON.stringify(headers, replacer, 2)}`);
+    out.push(`+ 'removeparam=' filters (${removeparams.length}): ${JSON.stringify(removeparams, replacer, 2)}`);
+    out.push(`+ Unsupported filters (${unsupported.length}): ${JSON.stringify(unsupported, replacer, 2)}`);
+    out.push(`+ generichide exclusions (${network.generichideExclusions.length}): ${JSON.stringify(network.generichideExclusions, replacer, 2)}`);
+    if ( result.specificCosmetic ) {
+        out.push(`+ Cosmetic filters: ${result.specificCosmetic.size}`);
+        for ( const details of result.specificCosmetic ) {
+            out.push(`    ${JSON.stringify(details)}`);
+        }
+    } else {
+        out.push('  Cosmetic filters: 0');
+    }
+    return out.join('\n');
+}
+
+
 /******************************************************************************/
 
 dom.on('#console-clear', 'click', ( ) => {
@@ -146,7 +241,7 @@ dom.on('#snfe-todnr', 'click', ev => {
     vAPI.messaging.send('devTools', {
         what: 'snfeToDNR',
     }).then(result => {
-        log(result);
+        log(toDNRText(result));
         dom.attr(button, 'disabled', null);
     });
 });
diff --git a/src/js/messaging.js b/src/js/messaging.js
index 0142a1261..d35a1347e 100644
--- a/src/js/messaging.js
+++ b/src/js/messaging.js
@@ -42,7 +42,6 @@ import {
 import cacheStorage from './cachestorage.js';
 import cosmeticFilteringEngine from './cosmetic-filtering.js';
 import { denseBase64 } from './base64-custom.js';
-import { dnrRulesetFromRawLists } from './static-dnr-filtering.js';
 import { filteringBehaviorChanged } from './broadcast.js';
 import htmlFilteringEngine from './html-filtering.js';
 import { i18n$ } from './i18n.js';
@@ -1897,95 +1896,15 @@ const onMessage = function(request, sender, callback) {
             ),
             env: vAPI.webextFlavor.env,
         };
-        const t0 = Date.now();
-        dnrRulesetFromRawLists(listPromises, options).then(result => {
-            const { network } = result;
-            const replacer = (k, v) => {
-                if ( k.startsWith('__') ) { return; }
-                if ( Array.isArray(v) ) {
-                    return v.sort();
-                }
-                if ( v instanceof Object ) {
-                    const sorted = {};
-                    for ( const kk of Object.keys(v).sort() ) {
-                        sorted[kk] = v[kk];
-                    }
-                    return sorted;
-                }
-                return v;
-            };
-            const isUnsupported = rule =>
-                rule._error !== undefined;
-            const isRegex = rule =>
-                rule.condition !== undefined &&
-                rule.condition.regexFilter !== undefined;
-            const isRedirect = rule =>
-                rule.action !== undefined &&
-                rule.action.type === 'redirect' &&
-                rule.action.redirect.extensionPath !== undefined;
-            const isCsp = rule =>
-                rule.action !== undefined &&
-                rule.action.type === 'modifyHeaders';
-            const isRemoveparam = rule =>
-                rule.action !== undefined &&
-                rule.action.type === 'redirect' &&
-                rule.action.redirect.transform !== undefined;
-            const runtime = Date.now() - t0;
-            const { ruleset } = network;
-            const good = ruleset.filter(rule =>
-                isUnsupported(rule) === false &&
-                isRegex(rule) === false &&
-                isRedirect(rule) === false &&
-                isCsp(rule) === false &&
-                isRemoveparam(rule) === false
-            );
-            const unsupported = ruleset.filter(rule =>
-                isUnsupported(rule)
-            );
-            const regexes = ruleset.filter(rule =>
-                isUnsupported(rule) === false &&
-                isRegex(rule) &&
-                isRedirect(rule) === false &&
-                isCsp(rule) === false &&
-                isRemoveparam(rule) === false
-            );
-            const redirects = ruleset.filter(rule =>
-                isUnsupported(rule) === false &&
-                isRedirect(rule)
-            );
-            const headers = ruleset.filter(rule =>
-                isUnsupported(rule) === false &&
-                isCsp(rule)
-            );
-            const removeparams = ruleset.filter(rule =>
-                isUnsupported(rule) === false &&
-                isRemoveparam(rule)
-            );
-            const out = [
-                `dnrRulesetFromRawLists(${JSON.stringify(listNames, null, 2)})`,
-                `Run time: ${runtime} ms`,
-                `Filters count: ${network.filterCount}`,
-                `Accepted filter count: ${network.acceptedFilterCount}`,
-                `Rejected filter count: ${network.rejectedFilterCount}`,
-                `Un-DNR-able filter count: ${unsupported.length}`,
-                `Resulting DNR rule count: ${ruleset.length}`,
-            ];
-            out.push(`+ Good filters (${good.length}): ${JSON.stringify(good, replacer, 2)}`);
-            out.push(`+ Regex-based filters (${regexes.length}): ${JSON.stringify(regexes, replacer, 2)}`);
-            out.push(`+ 'redirect=' filters (${redirects.length}): ${JSON.stringify(redirects, replacer, 2)}`);
-            out.push(`+ 'csp=' filters (${headers.length}): ${JSON.stringify(headers, replacer, 2)}`);
-            out.push(`+ 'removeparam=' filters (${removeparams.length}): ${JSON.stringify(removeparams, replacer, 2)}`);
-            out.push(`+ Unsupported filters (${unsupported.length}): ${JSON.stringify(unsupported, replacer, 2)}`);
-            out.push(`+ generichide exclusions (${network.generichideExclusions.length}): ${JSON.stringify(network.generichideExclusions, replacer, 2)}`);
-            if ( result.specificCosmetic ) {
-                out.push(`+ Cosmetic filters: ${result.specificCosmetic.size}`);
-                for ( const details of result.specificCosmetic ) {
-                    out.push(`    ${JSON.stringify(details)}`);
-                }
-            } else {
-                out.push('  Cosmetic filters: 0');
-            }
-            callback(out.join('\n'));
+        import('./static-dnr-filtering.js').then(module => {
+            const t0 = Date.now();
+            module.dnrRulesetFromRawLists(listPromises, options).then(dnrdata => {
+                dnrdata.listNames = listNames;
+                dnrdata.runtime = Date.now() - t0;
+                callback(s14e.serialize(dnrdata));
+            })
+        }).catch(reason => {
+            callback(reason);
         });
         return;
     }