So you want to play Starfinder! That's great! However, if your only experience with TTRPGs is mostly limited to D&D 5e (referred to as 5e from here on), there's going to be some differences, which I'll outline here.

Disclaimer: I've done my best to be as accurate as possible, but in the event of a rules conflict, your GM knows best, followed by the Core Rulebook. Do not rely on this document to be a comprehensive guide.

If you want a brief overview, an auto-generated table of contents is available in the top left:

Let's get started!

Starfinder determines the result of "checks" much like D&D: you roll a d20, add modifiers (bonuses and penalties), and if the number matches or exceeds the difficulty class (DC) or armor class (AC), the check succeeds. If not, the check fails. Like 5e, Starfinder has the same six ability scores (strength, dexterity, constitution, intelligence, wisdom, charisma). The modifier conversion is the same as well (a score of 10 is a modifier of +0, 8 is -1, and 12 is +1). And there are saving throws, ability checks, attack rolls, and skill checks that add your ability modifier. In fact, ability checks are exactly the same: roll a d20, and add your ability modifier. However, the similarities mostly end there.

Let's start with Saving Throws. Instead of having a saving throw for each ability score, there are now only three types of saving throws: Fortitude, Reflex, and Will, corresponding to Constitution, Dexterity, and Wisdom saving throws respectively. All other saving throws are equivalent to one of these, or to a skill or ability check. Like 5e, succeeding at a saving throw either negates entirely or partially negates an adverse effect. But unlike 5e, characters are not considered "proficient" or "not proficient" in saving throws. Rather, your class determines a base saving throw modifier for each type of saving throw at each level.

Likewise, since Starfinder does not have the concept of a "proficiency bonus," attack rolls are affected by what's called a "Base Attack Bonus" (BAB), determined by your class in a similar fashion to the saving throw bonuses. In addition, attack rolls also are affected by your strength or dexterity modifier, depending on the weapon being used. Be aware: spells that roll to attack, unless stated otherwise, use either the strength or dexterity modifier depending on whether it's melee range.

Skill checks are the most involved. Your total skill bonus consists of:

• Skill Ranks: Each level-up, you can spend skill ranks (earned based on intelligence modifier and class) on your skills, investing no more ranks total than your current level. Each rank provides a +1 bonus to the total skill bonus.
• Trained Class Skill Bonus: Your class defines what skills are considered "class skills." If at least one skill rank is invested in a class skill, it becomes a trained class skill, providing an additional +3 bonus.
• Associated Ability Score Modifier: Each skill has an associated ability score. You'll recognize some skills (Athletics, Stealth, Perception) which will have the same associated ability (strength, dexterity, and wisdom for the aforementioned), but others will not be familiar to you. The ability score modifier is added to the total skill bonus.
• Other Modifiers: Your character's race, items, feats, spell effects, and circumstances can all factor into the total skill bonus. Of particular note is the "armor check penalty." Certain skills (Acrobatics, Athletics, Sleight of Hand, Stealth) are affected when you wear bulky armor. That armor will have an Armor Check Penalty (ACP) modifier that gets added to the total skill bonus. But these modifiers can be positive too; consider "Aid Another." If the GM allows, you can make a DC 10 skill check performing the same action as the character you're helping, and add a +2 bonus to their check if you succeed.

Another major difference in Starfinder is the Take 10 and Take 20 rule for skill checks. If you are not in immediate danger or distracted, the GM can allow you to take 10 on the skill check, meaning your score is the total you would get as if you had rolled a 10. The idea is that routine and simple tasks for your character are hard to fail.

Taking 20 is like taking 10, but it means that you have plenty of time to devote to the task (20 times as long as the time for a single check) and it assumes that you are failing multiple times before you succeed. The upside is that instead of 10 plus your total skill bonus, it's 20.

Starfinder is much more specific than 5e about specific situations. As such, instead of granting advantage when a character is more likely to succeed or disadvantage when a character is more likely to fail, Starfinder bestows more bonuses and penalties. So how should you understand what a "+2" bonus means when in 5e you would receive advantage in a similar situation?

Consider the following chart:

It shows the numerical bonus or penalty of advantage and disadvantage in 5e, at different DCs and assuming a modifier of +0. For example, if you have advantage against a DC 10 check, that's equivalent to a +4.95 (+5) bonus. However, if you have advantage against a DC 18 check, that's only a +2.55 (+3) bonus.

Starfinder however is linear in its bonuses and penalties. If you have a +3 bonus, it applies equally regardless if the DC is 10 or 18.

That's not the only difference. When 5e does add modifiers instead of advantage, they all combine together. Starfinder is like this, mostly. But sometimes only certain bonuses can take effect. This is because of bonus types, found on page 266 of the Core Rulebook (CRB). For example, two morale bonus types won't stack, even if they come from different sources, because you can only have one thing affecting your morale. The notable exception to this is circumstantial bonuses, which can stack if they are because of different circumstances. Do note, penalties and bonuses do not interact, and penalties often do stack when they are of different causes.

Starfinder has a great guide to the steps of character building in the Core Rulebook, Chapter 2 (page 14). Broadly speaking, there are three major components to your character: class, race, and theme. Optionally, there are archetypes, but if this is your first time playing Starfinder I recommend against them.

There are currently (as of end of 2022) thirteen classes in Starfinder. Of these, I recommend the classes in the core rulebook (Envoy, Mechanic, Mystic, Operative, Solarian, Soldier, and Technomancer) for new players. New players may also consider the classes in the Character Operations Manual (Biohacker, Vanguard, Witchwarper) if they're feeling spicy or if it's a better fit for them, with the awareness that there are less guides and information sources out there on the internet for them.

Classes universally determine several key statistics and numbers:

• Key Ability Score: This is the ability score that most, if not all, of your class abilities will depend on. The higher it is, the more powerful your class abilities are. In addition, your number of Resolve Points will depend on this score. Your Resolve Points help keep you from dying and are a resource for advanced abilities. Your key ability score should always be your highest ability score.
• Hit Points and Stamina Points per Level: While we'll get into the specifics of hit points and stamina points in the Life and Death section of the Combat section, just know that the more you have, the harder you are to take down.
• Skill Ranks per Level: All classes gain "some number" plus your intelligence modifier of skill ranks per level. That "some number" represents how skill oriented your class is. Generally, 8 is the higher end and 4 is the lower end for this number.
• Class Skills: These are the skills your class is proficient in. In other words, you gain a +3 bonus to that skill if you have a skill rank in it. In other words, it provides an edge that other classes may not get.
• Armor and Weapon Proficiencies: Your class will define what armors and weapons you will be proficient in. The summary is that if you wear an armor or wield a weapon you are not proficient in, you take a -4 penalty to the related checks and DCs (Armor Class, attack rolls, and DCs of saving throws for that weapon). Oof! Keep in mind, you can normally only gain proficiencies through feats.
• Weapon Specializations: Proficiencies are punishing if you don't have them. Conversely, specializations are rewarding if you do have them. Every class gains specializations for their weapon proficiencies in at 3rd level (other than grenades). For small arms and operative melee weapons, you get half your character level rounded down added to your damage. For other weapons, you get your character level added to your damage. Nice! Like proficiencies, weapon specializations are normally only earned through feats.
• Base Attack Bonus: Instead of all classes having the same proficiency bonus that's added to your attack roll (like in 5e), Starfinder has a Base Attack Bonus (BAB). Depending on your class, you will have either a BAB that scales 1:1 with your level (at level 8 you have a +8 bonus), or a BAB that scales 3/4 of your level rounded down (at level 8 you have a +6 bonus). A BAB scaling 1:1 typically means your class is oriented more towards straight attacking with weapons in combat.
• Save Bonuses: Instead of having individual saving throws per ability score, there are only three types of saving throws: Fortitude, Reflex, and Will. And instead of proficiencies, your save bonus determines what additional numbers you add to your saving throw (in addition to the matching ability score modifiers of Constitution, Dexterity, and Wisdom respectively). There are two types of progressions of save bonuses: Good and Poor (my terms). There's no clear mathematical pattern to them, but generally each class will have one or two Good progressions, and at least one Poor progression. Spellcasters tend to have only one Good progression of save bonuses compared to other classes.

All classes will also grant special abilities. These abilities usually have a classification of one of the following:

• Extraordinary Abilities (Ex)
• Spell-Like Abilities (Sp)
• Supernatural Abilities (Su)

These classifications are further described on page 262 of the core rulebook. Here's the quick and dirty rundown though:

In addition, certain classes will have spellcasting. Spellcasters (currently Mystic, Precog, Technomancer, and Witchwarper) will have a limited number of spell slots per day. Like in 5e, spell slots are regained through extended rest, specifically, 8 hours of continuous rest and 15 minutes of concentration after this rest period.

All spellcasters will have a limited library of spells they pick out every level up. However, unlike 5e you do not have to "prepare" spells ahead of time. All the spells you know can be cast as long as you have the requisite spell slot.

Like D&D, race is more a representation of species. There are many, many races/species in Starfinder. Of course, you have the typical D&D races (Dwarves, Elves, Gnomes, Half-Elves, Half-Orcs, and Halflings, found on page 506 in the core rulebook), but the more common races in the Pact Worlds (the core setting of Starfinder) are Androids, Humans, Kasathas, Lashuntas, Shirrens, Vesk, and Ysoki. Beyond that, there are even more options, but generally each race can be boiled down to some core concepts.

• Size and Type: Most races in Starfinder are a small or medium humanoid with a subtype specific to their race. However, this is not always the case.
• Hit Points: At level 1, your starting HP is equal to the hit points here added to the hit points in your class description.
• Racial Traits: Your race will have various positive and rarely sometimes negative abilities.
• Lore: This is the section that describes the culture and personalities common in the race. It may mention here as well if there are specific languages common to the race.

In addition, some sourcebooks will have additional options for specific races. The Character Operations Manual, for instance, has additional racial traits that can be swapped out for the core rulebook races.

Theme corresponds with 5e's backgrounds, though theme in Starfinder is a little more impactful and present. Your theme represents an element of your character's backstory, as well as your character's focus. All themes provide the following:

• Ability Score Adjustment: Each theme provides a +1 adjustment to one of your ability scores at character creation.
• Bonus Class Skill: At first level, a skill relevant to the theme is provided either as a class skill or, if it is already a class skill from your current class, a flat +1 bonus.
• Theme Knowledge: You are granted a bonus to a subset of skill checks for a specific skill. This can take many forms however, such as Bounty Hunter's bonus to information on a specific target.
• Special Benefits: There are additional benefits granted by the theme at 6th, 12th, and 18th level.

Starfinder is a much more tactical game than 5e. By this, I mean that in Starfinder, location, movement, cover, etc. are much more impactful and consequential. In other words, there are less options to directly deal damage, and more options to improve your chances to deal damage.

Because "advantage" and "disadvantage" are not things in Starfinder, and since circumstantial bonuses and penalties can stack, you can and are expected to use every edge you have to apply bonuses to yourself and penalties to your enemies. And the rules reflect this. There are bonuses for flanking, bonuses for different types of cover, penalties for being surprised, penalties for being knocked off-kilter in zero-gravity, and so on and so forth.

You cannot and will not remember each source of bonus or penalty. But you can have your character specific bonuses marked down on your character sheet, and bring up the sources in question as needed. From there, the GM can determine the resulting bonuses and penalties.

Here is a handy cheatsheet for combat actions: https://www.reddit.com/r/starfinder_rpg/comments/fuwi0j/oc_starfinder_cheat_sheet/ I've reposted it here as well:

Many of the actions in Starfinder are similar to those in 5e. However, they are not the same. Some key differences:

• Movement cannot normally be split around an attack. Either you move then attack, or attack then move.
• Full actions are used in place of your standard action, move action, and swift action. There's no comparable "uber-action" in 5e.
• Attacks of opportunity are provoked by any movement out of a threatened square other than a guarded step (move action) or the first step of a withdraw action (full action). Note, by "any" this means forced movement of any kind provokes attacks of opportunity, and "square" means that even if you remain in the threat zone of the opponent, simply moving out of a threatened square provokes the attack of opportunity.
• Attacks of opportunity are also provoked by ranged attacks and spells/spell-like abilities, unless noted otherwise.
• Recovering from being prone (standing up) is normally a move action.
• Standard actions cannot be converted to extra movement speed, other than through full actions (run and withdraw). Combined with the previous point, this means that unless you have one of the Kip-Up feats, you cannot stand up from prone and move on the same turn.
• Drawing your weapon consumes your movement action unless you have a base attack bonus of +1 or higher. This doesn't matter much past levels 1 and 2.

For spellcasters,

• Concentrating on a spell is much more taxing. Each round, you must spend your standard action to concentrate on the spell.
• Dismissing a spell is much more taxing as well; it takes a standard action to dismiss a spell. However, dismissing a concentration spell does not cost a standard action, as dismissing it just means not concentrating on it.

In addition, there are several actions/full actions that aren't in 5e (charge, fight defensively, several of the combat maneuvers).

Starfinder is very different from 5e in that healing is not nearly as critical. This is because you have two health pools, Stamina Points (SP) and Hit Points (HP). In addition, your character will have a number of Resolve Points, which are related but not equivalent to health. Your SP are generally very comparable to your HP in terms of size, but they regenerate much more quickly. They are also where damage is typically allocated first. The quickest way to restore them is by spending 1 Resolve Point during a 10-minute uninterrupted rest (the equivalent of the 1-hour 5e short rest).

HP on the other hand regenerates much slower than HP in 5e, which is quite significant. For example, after an 8-hour rest, all SP and Resolve Points are restored, but only 1 HP per level is restored. At level 1 for an Ysoki Technomancer (one of the lowest starting HP builds), that's still only 1/7 of their total HP. So think of HP like your capacity for wounds, and SP as your readiness and energy.

The rules for dying, stabilization, and death are quite different from 5e. However, the similarities are:

• If you're stable, you're safe and at 0 HP for now. However, Starfinder makes long term stability without healing much more dangerous, requiring a Constitution check after 1 hour.
• If you take damage reducing you to 0 HP, if the remaining damage exceeds your maximum health, you die instantly.
• Healing a character that is dying or stable brings them back up, as if they had never been reduced to 0 HP.

Read page 250 in the CRB for more information on death and dying, but the basic idea is if you are at 0 HP and 0 Resolve Points, you are dead.

While the Galactic Magic sourcebook (GMG) has partially addressed this, the fact is that level 0 spells (equivalent to cantrips in 5e) will not usually cut it for dealing damage as a spell caster. Some higher level spells can deal a fair bit of damage, but remember the universe: why take the years of training to learn fireball when you can go out and buy a rocket launcher tomorrow? Magic is not a good source of damage in most cases. Rather, it is largely meant to improve your chances on and off the battlefield.

So if magic isn't what causes damage, what does? Grenades. Guns. Grenade guns. Big hitty sticks. Small pokey things. Basically, any weapon you could imagine, it's there. And like any gun, the bigger guns deal more damage than the smaller guns.

This is a problem for some classes that only have proficiency in Small Arms. Unless you're the operative, Small Arms (one-handed guns) will deal much less damage than Longarms (light two-handed guns). My recommendation is to get a longarm and get proficiency in a longarm with your first feat.

By gear, I mean weapons, armor, armor upgrades, augmentations, weapon fusions, tech items, magic items, hybrid items, drugs, etc.

Impact: Absolutely necessary.

This is your primary source of information.

• Basic rules (character creation, leveling up, combat, starship combat, equipment)
• Classes: Envoy, Mechanic, Mystic, Operative, Solarian, Soldier, Technomancer
• Basic lore about the setting (Pact Worlds centric, but mentions of other systems)

Impact: Adds flexibility and more options. Very significant.

• Three new classes: Biohacker, Vanguard, and Witchwarper
• Class options (envoy, mechanic, mystic, operative, solarian, soldier, technomancer)
• New gear: shields and injection weapons in particular among others
• Extra rules for starship combat, in particular new roles for STR and WIS characters which suffered without them
• Race options for CRB races
• New spells (mystic, technomancer)
• New themes
• New archetypes

Impact: Useful if you want more options with gear.

• Greatly expands number of sniper weapons available
• Adds many other options for gear
• Class options (envoy, mechanic, mystic, operative, solarian, soldier, technomancer)

Impact: Adds more tech and new mechs, but "if you really want to play with mechs find another TTRPG" is what I've heard.

• New class: Nanocyte
• Class options: (biohacker, envoy, mechanic, mystic, operative, solarian, soldier, technomancer, vanguard, witchwarper)
• Mech rules
• New gear
• Lore about tech

Impact: Can be significant for spell-casters.

• New class: Precog
• Class options: (biohacker, envoy, mechanic, mystic, nanocyte, operative, solarian, soldier, technomancer, vanguard, witchwarper)
• New gear
• New spells (mystic, technomancer, witchwarper)
• Variant spell-casting: big boost for level-0 combat spells if your GM permits
• Lore about magic
• New archetype