diff --git a/lib/config.ts b/lib/config.ts
index e19ab2b50..077dcf19a 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -67,6 +67,7 @@ type ConfigEnvKeys =
     | 'DISABLE_NSFW'
     | 'SUFFIX'
     | 'TITLE_LENGTH_LIMIT'
+    | 'FORMAT'
     // OpenAI
     | 'OPENAI_API_KEY'
     | 'OPENAI_MODEL'
@@ -340,6 +341,7 @@ export type Config = {
     };
     suffix?: string;
     titleLengthLimit: number;
+    format: string;
     openai: {
         apiKey?: string;
         model?: string;
@@ -842,6 +844,7 @@ const calculateValue = () => {
         },
         suffix: envs.SUFFIX,
         titleLengthLimit: toInt(envs.TITLE_LENGTH_LIMIT, 150),
+        format: envs.FORMAT || 'rss',
         openai: {
             apiKey: envs.OPENAI_API_KEY,
             model: envs.OPENAI_MODEL || 'gpt-3.5-turbo-16k',
diff --git a/lib/middleware/cache.ts b/lib/middleware/cache.ts
index fe5acf34d..0a9d28cb8 100644
--- a/lib/middleware/cache.ts
+++ b/lib/middleware/cache.ts
@@ -19,7 +19,7 @@ const middleware: MiddlewareHandler = async (ctx, next) => {
     }
 
     const requestPath = ctx.req.path;
-    const format = `:${ctx.req.query('format') || 'rss'}`;
+    const format = `:${ctx.req.query('format') || config.format}`;
     const limit = ctx.req.query('limit') ? `:${ctx.req.query('limit')}` : '';
     const key = 'rsshub:koa-redis-cache:' + h64ToString(requestPath + format + limit);
     const controlKey = 'rsshub:path-requested:' + h64ToString(requestPath + format + limit);
diff --git a/lib/middleware/template.tsx b/lib/middleware/template.tsx
index ecc947ee5..8983b8c2d 100644
--- a/lib/middleware/template.tsx
+++ b/lib/middleware/template.tsx
@@ -20,7 +20,7 @@ const middleware: MiddlewareHandler = async (ctx, next) => {
     }
 
     const data: Data = ctx.get('data');
-    const outputType = ctx.req.query('format') || 'rss';
+    const outputType = ctx.req.query('format') || config.format;
 
     // only enable when debugInfo=true
     if (config.debugInfo) {