- 该国全部的科技等级之总和（ 行政科技、 外交科技、 军事科技）落后临近的西欧科技组国家科技总和至少7级。
- 该国至少拥有 0点稳定度。
- 该国没有 过度扩张。
- New World natives with the Tribal Council government must also reform the government before westernization.
- New World states following the Inti, Mayan and Nahuatl religions must fully reform them before westernization.
- An AI country cannot be a protectorate
- One of the following conditions must be true:
- The country owns and has a core on a core province of a western nation.
- The country has a core province bordering a core province of a western nation that is not assigned to a trade company. This effectively rules out westernizing by neighboring a western core province in Africa, with the exception of North Africa.
- The High American tech group, only appearing in Random New Worlds with fantasy elements ( Conquest of Paradise DLC required) or in converted Crusader Kings II saves with the Sunset Invasion DLC active, is considered Western for the purpose of allowing other states to westernize. A country westernizing this way becomes Western, not High American.
Once westernization begins, loss of the western core or border will not cancel the process. Unlike previous versions, diplomatic annexation has no effect on westernization and vice versa.
Another way to westernize is by the Western Focus decision. Taking this decision will immediately change the country's technology group to Western. 通过西方焦点决议西化需要满足以下条件：
- 东欧或 安纳托利亚科技组
- 至少 1 稳定度
- 至少300 发展度
- 至少为 王国级
A nation also requires a certain province as core with less than 1 separatism. For nations with an East Slavic or Finno-Ugric culture, either Danzig or Krakow is needed. For other nations, either Vienna or Prague is needed.
Westernization costs Monarch Power equal to 2000 modified by the tech penalty of the country's technology group prior to westernizing. (For example, westernization of an Eastern tech nation will require 2000 * 1.2 = 2400 power points in total.) If available, each month, up to 10 points are drained from each Monarch Power type and added to the progress. The number of points of Monarch Power drained each month is reduced by 1 for each 100 total development, down to a minimum of 5 points per Monarch Point type for a country with more than 500 development. Thus, powerful countries will westernize more slowly. If the player's monarch points reach 0 in any category, westernization will only take as many points as the country produces, unless of course the points produced are higher than the progress per month per category. If the player's monarch points fall below 0 in any category (for example, through an event), that category will contribute 0 points to westernization progress until the player's monarch points in that category are 0 or greater again.
During the westernization process, the country has the following effects:
- +5% unrest caused by Western Influences modifier
- +50% advisor cost.
- 西化事件 giving a choice between losing 120 points of progress or another penalty occur every year. Other penalties include loss 100 admin, diplomatic or military monarch points, loss of legitimacy, loss of prestige, loss of army tradition and reactionary, nationalist or religious rebels. Reactionary rebels winning a siege, either in a province with a fort, or in a province that is not in the zone of control of a fort, will reduce westernization progress slightly.
- Totemist, Shamanist and Animist pagans may get an event to convert to Christianity, which gives access to useful decisions and easier diplomacy with Europeans.
- Ming will lose its Mandate of Heaven (-5% unrest and -10% stability cost)
Westernization can be paused through the technology screen. This will pause the draining of monarch power and pause progress, allowing the player to recover monarch points (e.g., to increase stability). Westernization events will also not fire while the progress is paused. The westernization effects remain the same otherwise.
During westernization, reactionary rebels can spawn and demand the cancellation of the westernization attempt.
- If these rebels break the country or if their demands are accepted, Westernization will be canceled and all progress lost.
- After westernization completes, reactionaries are still a rebel faction though they cannot reverse the process.
- The negative effects that were present during westernization are removed upon its completion.
- However, the nation continues to use and produce units from its previous technology group.
- The cap for monarch points will drop to 999, the standard cap for western technology. If the player has over 999 accumulated points in any Monarch Point pool when westernization completes, they will be cut down to 999 (no longer true in the latest patch).
- Nations that were previously able to be vassalized might now only be able to be protectorates, if the tech level difference is too great.
The first encounter with the European powers usually happens when reforming religion is already possible. This gives a huge boost to the current technology levels (not the cost of technology) to 80% of the Western neighbor (this may already make the player competitive in terms of military strength with its new neighbors). This implies that buying technology prior to this is technically a waste of monarch power beyond the basic levels needed to expand and to compete with the player's neighbors. This usually means level 5 and level 3, for unlocking the first idea group (Exploration) and filling it. It may still be necessary to advance in military technology, in order not to fall behind the player's enemies in that category.
While waiting to make contact with a Western neighbor, monarch points are best spent on anything other than technology if the player is close to reaching the cap. This includes increasing stability to at least 1, increasing the development of provinces (despite the penalty to natives in that category) and converting culture. Take note that the latter may be redundant once the player reaches empire government rank and becomes a cultural union.
Westernization drops by -3 and will have a constant drain on monarch points and fire events that will give a choice of losing 100 monarch points in category or stability, or losing progress. Additionally, the player will still receive regular events which may deduct monarch points or decrease stability. As such, they should prepare by stockpiling monarch points; the weaker the ruler, the more monarch points should be stockpiled. The player should also keep in mind that they must immediately increase stability to at least 0 once Westernization is started, to avoid adding to the negative effects of Westernization. The Westernization button, once pressed, will turn into a progress bar that tells the player how much monarch power is drained per month from each category, and when completion is expected.
Rebels can be a serious problem during westernization. As such, it is advisable to start the process with near full manpower and have a stockpile of gold. If the country is relatively large, armies and navies should be distributed strategically to deal with rebels as they spawn. Highest priority should be reactionary rebels, as they will slow down westernization progress, and nationalist or separatist rebels, as they may make the player lose provinces. Occupied provinces will also reduce player income (and possibly manpower or trade power), and rebels taking a province usually have a negative effect on the province (cf. Rebel factions for details). If the country's religion is pagan, one of the events likely to fire is to change to the religion of the western neighbor. If the decision is accepted, the changed religion reduces the religious unity to 0, driving up the national unrest even higher, and making it highly likely that religious rebels will spawn.
Take note that low legitimacy or republican tradition increases unrest significantly - therefore, it is likely best to keep legitimacy or republican tradition high if at all possible, and rather slow westernization progress than accept events that lower legitimacy / republican tradition.
Unless the westernizing nation is of the Sub-Saharan technology group, they will likely have unlocked a second or third idea group. Any idea that will help with decreasing unrest or increasing tolerance will help keep unrest down during Westernization. A theologian advisor may also be useful during that period.
Finally, it is best to keep in mind that technologies will be significantly cheaper after Westernization is completed - as such, it is usually not a good investment to buy technology levels before the process is complete.