Only, a citizen of United Kingdom (UK) has the authority to request a visa for his/her spouse. You should be careful while applying for UK visa. That includes the legal marriage age restorations, financial stability, etc. The main reasons to apply for a UK spouse visa are as follows.
When you get the visa for your spouse, he or she can stay in the UK for next two years. After this, the visa needs to be reapplied or renewed as the case may be. The extension of Visa for a period not exceeding 30 months is also possible. When this extension is granted, your spouse is legally eligible to apply for British citizenship.
There is a special clause in UK immigration department known as the UK marriage visa, by this a person can stay in the UK on account of their spouse being settled in the UK. It is also called a spouse visa. With this visa, the spouse can stay in the UK indefinitely. The spouse is also allowed to work in the UK.
Those staying outside the UK, and the European Economic Area including Switzerland can apply for this visa at the British embassy, consulate or high commission nearest to them. Except for North Koreans, all others can apply online. Those staying in North Korea have to make a hard copy application.
Those who are already in the UK on any other visa including student Visa can apply for a UK marriage visa there. This is meant for those who are legally married or those who are going to get legally married. The cooling period called Further Leave to Remain shall apply. This enables the spouse 30 months within which to get a formal visa.
Kindly browse migrate-me.com/uk-spouse-visa.php for more details on the main reasons to apply for a UK spouse visa.