How to find a URL that can download YouTube videos fast?

The URL of the video is described in the HTML source of YouTube.

For example, the following is a video of 360p(itag=18) fromhttps://www.youtube.com/watch?v=g25V7k3J8p0.

https://rr3---sn-ogul7n7d.googlevideo.com/videoplayback?expire=1663411914&ei=alIlY_zbLLCSvcAPweKB8Ao&ip=240b:c010:460:7f43:28ad:44fc:a7fd:a53d&id=o-APN7UpoL8PXUirzX2I1xN_IUB8QU0gPDCORsI4NT_HMj&itag=18&source=youtube&requiressl=yes&mh=_R&mm=31,26&mn=sn-ogul7n7d,sn-3pm7dnes&ms=au,onr&mv=m&mvi=3&pl=52&initcwndbps=616250&vprv=1&mime=video%2Fmp4&ns=7cE-kpoUrFkmuk9r8BM8XgcI&cnr=14&ratebypass=yes&dur=20.665&lmt=1662988960680381&mt=1663390140&fvip=1&fexp=24001373,24007246&c=MWEB&rbqsm=fr&txp=6219224&n=6nRCWhxcp2KdWwLa&sparams=expire,ei,ip,id,itag,source,requiressl,vprv,mime,ns,cnr,ratebypass,dur,lmt&sig=AOq0QJ8wRQIhAKlVetHQXpoD-ubRS8-zg4_011y5goeKzV3fCjP_COeQAiB3nBBjrh938ds8VBtZYZL2bck5Q8mPhaxI5KlKj4f1pg==&lsparams=mh,mm,mn,ms,mv,mvi,pl,initcwndbps&lsig=AG3C_xAwRQIhANDTDwOm_E07zyKhb3qUzp8dGKY_hZr1-2vK_EwoedPcAiA3QHQXSg2FXn4bfcHBcMdlGG-gt3lLnX3zX80wUVQrmg==

But when I try to download this url it is slow. 70KB/s.

On the other hand, if I use a YouTube download site (such as https://en.savefrom.net), the following URL will be extracted.

https://rr1---sn-g530uxow2-ioqe.googlevideo.com/videoplayback?expire=1663412082&ei=ElMlY7jaGu2W2LYP3c2oqAM&ip=216.131.72.113&id=o-AFJFK2pnbiZoSpWLuAu79M0maZb3Qu5xdfDF-_6Ss2Ai&itag=18&source=youtube&requiressl=yes&spc=yR2vp1IgjyLsy4bpI3T537Nm15qgPPU&vprv=1&mime=video%2Fmp4&ns=pQxTog8SEWaLin2xwX5b0JYI&cnr=14&ratebypass=yes&dur=20.665&lmt=1662988960680381&fexp=24001373,24007246&c=WEB&rbqsm=fr&txp=6219224&n=l4yqz7hi7FyuEg&sparams=expire%2Cei%2Cip%2Cid%2Citag%2Csource%2Crequiressl%2Cspc%2Cvprv%2Cmime%2Cns%2Ccnr%2Cratebypass%2Cdur%2Clmt&sig=AOq0QJ8wRQIgAs27z4CdSe0ChuDn_Mp5eZXitU-p68VU99nRA1fGE7ECIQCCRuTAXMkcafvIW7HgrLLhNUeriEu4cuMkbxviDBTpdA%3D%3D&redirect_counter=1&rm=sn-p5qeel7s&req_id=d2af52c30e3ca3ee&cms_redirect=yes&cmsv=e&ipbypass=yes&mh=_R&mip=240b:c010:460:7f43:28ad:44fc:a7fd:a53d&mm=31&mn=sn-g530uxow2-ioqe&ms=au&mt=1663390375&mv=u&mvi=1&pl=52&lsparams=ipbypass,mh,mip,mm,mn,ms,mv,mvi,pl&lsig=AG3C_xAwRgIhAJNVc1DLA8nH-SGMAH4cvvlF8uessMGq4T9_cGjStzuRAiEAzxZVHI-lbgwk891NMHOv2GifcQmjhph6M2aoithxjvQ%3D

This URL downloads fast. 1MB/s or more. This URL is not found in YouTube's HTML source.

Where can I find this URL?