diff --git a/core/interfaces.go b/core/interfaces.go
index ce2d25f..a8e4301 100644
--- a/core/interfaces.go
+++ b/core/interfaces.go
@@ -8,9 +8,9 @@ type Updater interface {
 	// ParseUpdate takes an unparsed interface{} (as a map[string]interface{}), and returns an Updater for a mod file.
 	// This can be done using the mapstructure library or your own parsing methods.
 	ParseUpdate(map[string]interface{}) (interface{}, error)
-	// CheckUpdate checks whether there is an update for each of the mods in the given slice,
+	// CheckUpdate checks whether there is an update for each of the mods in the given slice, for the given MC version,
 	// called for all of the mods that this updater handles
-	CheckUpdate([]Mod) ([]UpdateCheck, error)
+	CheckUpdate([]Mod, string) ([]UpdateCheck, error)
 	// DoUpdate carries out the update previously queried in CheckUpdate, on each Mod's metadata,
 	// given pointers to Mods and the value of CachedState for each mod
 	DoUpdate([]*Mod, []interface{}) error
@@ -31,7 +31,6 @@ type UpdateCheck struct {
 	Error error
 }
 
-// TODO: new docs
 // to carry out updating:
 
 // go through all metafiles in index
diff --git a/curseforge/curseforge.go b/curseforge/curseforge.go
index 7ccaf5e..081971f 100644
--- a/curseforge/curseforge.go
+++ b/curseforge/curseforge.go
@@ -1,6 +1,7 @@
 package curseforge
 
 import (
+	"errors"
 	"fmt"
 	"regexp"
 	"strconv"
@@ -198,16 +199,91 @@ func (u cfUpdater) ParseUpdate(updateUnparsed map[string]interface{}) (interface
 	return updateData, err
 }
 
-func (u cfUpdater) CheckUpdate(mod []core.Mod) ([]core.UpdateCheck, error) {
-	return nil, nil
+type cachedStateStore struct {
+	modInfo
+	fileInfo modFileInfo
 }
 
-func (u cfUpdater) DoUpdate(mod []*core.Mod, cachedState []interface{}) error {
-	// TODO: implement updating
-	// modInfoData, err := getModInfo(u.ProjectID)
-	// if err != nil {
-	// 	return false, err
-	// }
+func (u cfUpdater) CheckUpdate(mods []core.Mod, mcVersion string) ([]core.UpdateCheck, error) {
+	results := make([]core.UpdateCheck, len(mods))
+
+	// TODO: make this batched
+	for i, v := range mods {
+		projectRaw, ok := v.GetParsedUpdateData("curseforge")
+		if !ok {
+			results[i] = core.UpdateCheck{Error: errors.New("couldn't parse mod data")}
+			continue
+		}
+		project := projectRaw.(cfUpdateData)
+		modInfoData, err := getModInfo(project.ProjectID)
+		if err != nil {
+			results[i] = core.UpdateCheck{Error: err}
+			continue
+		}
+
+		updateAvailable := false
+		fileID := project.FileID
+		fileInfoObtained := false
+		var fileInfoData modFileInfo
+
+		for _, file := range modInfoData.GameVersionLatestFiles {
+			// TODO: change to timestamp-based comparison??
+			// TODO: manage alpha/beta/release correctly, check update channel?
+			// Choose "newest" version by largest ID
+			if file.GameVersion == mcVersion && file.ID > fileID {
+				updateAvailable = true
+				fileID = file.ID
+			}
+		}
+
+		if !updateAvailable {
+			results[i] = core.UpdateCheck{UpdateAvailable: false}
+			continue
+		}
+
+		// The API also provides some files inline, because that's efficient!
+		for _, file := range modInfoData.LatestFiles {
+			if file.ID == fileID {
+				fileInfoObtained = true
+				fileInfoData = file
+			}
+		}
+
+		if !fileInfoObtained {
+			fileInfoData, err = getFileInfo(project.ProjectID, fileID)
+			if err != nil {
+				results[i] = core.UpdateCheck{Error: err}
+				continue
+			}
+		}
+
+		results[i] = core.UpdateCheck{
+			UpdateAvailable: true,
+			UpdateString:    v.FileName + " -> " + fileInfoData.FileName,
+			CachedState:     cachedStateStore{modInfoData, fileInfoData},
+		}
+	}
+	return results, nil
+}
+
+func (u cfUpdater) DoUpdate(mods []*core.Mod, cachedState []interface{}) error {
+	// "Do" isn't really that accurate, more like "Apply", because all the work is done in CheckUpdate!
+	for i, v := range mods {
+		modState := cachedState[i].(cachedStateStore)
+
+		v.FileName = modState.fileInfo.FileName
+		v.Name = modState.Name
+		v.Download = core.ModDownload{
+			URL: modState.fileInfo.DownloadURL,
+			// TODO: murmur2 hashing may be unstable in curse api, calculate the hash manually?
+			// TODO: check if the hash is invalid (e.g. 0)
+			HashFormat: "murmur2",
+			Hash:       strconv.Itoa(modState.fileInfo.Fingerprint),
+		}
+
+		v.Update["curseforge"]["ProjectID"] = modState.ID
+		v.Update["curseforge"]["FileID"] = modState.fileInfo.ID
+	}
 
 	return nil
 }
diff --git a/curseforge/install.go b/curseforge/install.go
index 3291bce..479efc3 100644
--- a/curseforge/install.go
+++ b/curseforge/install.go
@@ -125,7 +125,7 @@ func cmdInstall(flags core.Flags, mod string, modArgsTail []string) error {
 	fileInfoObtained := false
 	var fileInfoData modFileInfo
 	if fileID == 0 {
-		// TODO: how do we decide which version to use?
+		// TODO: change to timestamp-based comparison??
 		for _, v := range modInfoData.GameVersionLatestFiles {
 			// Choose "newest" version by largest ID
 			if v.GameVersion == mcVersion && v.ID > fileID {