I am developing steam website for the first time. My development language is PHP . I have read this topic , I have done as exact as defined there. I am saving cookies and session id into database and using those to send tradeoffer. I am not using any script / library to send tradeoffer . Simply using curl to send tradeoffer and after 2 days this cookies don't work. this is my code to send tradeoffer. function makeOffer($sessionId, $cookies, $partner, $message = '', $token, $assetid_them, $steam_id) { $type = 'POST'; $url = 'https://steamcommunity.com/tradeoffer/new/send'; $data= array ( 'sessionid' => $sessionId, 'serverid' => '1', 'partner' => $steam_id, 'tradeoffermessage' => $message, 'trade_offer_create_params' => '{"trade_offer_access_token": "'.$token.'"}', 'json_tradeoffer' => '{"newversion":true,"version":2,"me":{"assets":[],"currency":[],"ready":false},"them":{"assets":['.$assetid_them.'],"currency":[],"ready":false}}' ); $c = curl_init(); curl_setopt($c, CURLOPT_HEADER, false); curl_setopt($c, CURLOPT_NOBODY, false); curl_setopt($c, CURLOPT_URL, $url); curl_setopt($c, CURLOPT_SSL_VERIFYHOST, 0); curl_setopt($c, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.0.3705; .NET CLR 1.1.4322)"); curl_setopt($c, CURLOPT_COOKIE, $cookies); curl_setopt($c, CURLOPT_POST, 1); curl_setopt($c, CURLOPT_POSTFIELDS, http_build_query($data)); curl_setopt($c, CURLOPT_RETURNTRANSFER, true); curl_setopt($c, CURLOPT_HTTPHEADER, array('Referer: https://steamcommunity.com/tradeoffer/new/?partner='.$partner.'&token='.$token)); curl_setopt($c, CURLOPT_SSL_VERIFYPEER, 0); curl_setopt($c, CURLOPT_FOLLOWLOCATION, 1); curl_setopt($c, CURLOPT_CUSTOMREQUEST, strtoupper($type)); $return = curl_exec($c); curl_close($c); return $return; } I am stuck at this moment If you could help me with some stuff or any suggestion , deeply appreciated. Thank you