diff --git a/pkg/mdformatter/linktransformer/link.go b/pkg/mdformatter/linktransformer/link.go
index 2f6044f..b59cafb 100644
--- a/pkg/mdformatter/linktransformer/link.go
+++ b/pkg/mdformatter/linktransformer/link.go
@@ -125,7 +125,7 @@ type validator struct {
 	c           *colly.Collector
 
 	futureMu    sync.Mutex
-	destFutures map[futureKey]*futureResult
+	destFutures sync.Map
 }
 
 type futureKey struct {
@@ -156,14 +156,13 @@ func NewValidator(ctx context.Context, logger log.Logger, linksValidateConfig []
 		localLinks:     map[string]*[]string{},
 		remoteLinks:    map[string]error{},
 		c:              colly.NewCollector(colly.Async(), colly.StdlibContext(ctx)),
-		destFutures:    map[futureKey]*futureResult{},
 	}
 	// Set very soft limits.
 	// E.g github has 50-5000 https://docs.github.com/en/free-pro-team@latest/rest/reference/rate-limit limit depending
 	// on api (only search is below 100).
 	if err := v.c.Limit(&colly.LimitRule{
 		DomainGlob:  "*",
-		Parallelism: 100,
+		Parallelism: 5,
 	}); err != nil {
 		return nil, err
 	}
@@ -234,6 +233,11 @@ func MustNewValidator(logger log.Logger, linksValidateConfig []byte, anchorDir s
 }
 
 func (v *validator) TransformDestination(ctx mdformatter.SourceContext, destination []byte) (_ []byte, err error) {
+	select {
+	case <-ctx.Context.Done():
+		return nil, ctx.Err()
+	default:
+	}
 	v.visit(ctx.Filepath, string(destination), ctx.LineNumbers)
 	return destination, nil
 }
@@ -242,7 +246,14 @@ func (v *validator) Close(ctx mdformatter.SourceContext) error {
 	v.c.Wait()
 
 	var keys []futureKey
-	for k := range v.destFutures {
+	// Read map from sync.Map.
+	destFuturesMap := map[futureKey]*futureResult{}
+	v.destFutures.Range(func(key, value interface{}) bool {
+		destFuturesMap[key.(futureKey)] = value.(*futureResult)
+		return true
+	})
+
+	for k := range destFuturesMap {
 		if k.filepath != ctx.Filepath {
 			continue
 		}
@@ -263,7 +274,7 @@ func (v *validator) Close(ctx mdformatter.SourceContext) error {
 	}
 
 	for _, k := range keys {
-		f := v.destFutures[k]
+		f := destFuturesMap[k]
 		if err := f.resultFn(); err != nil {
 			if f.cases == 1 {
 				merr.Add(errors.Wrapf(err, "%v:%v", path, k.lineNumbers))
@@ -279,11 +290,16 @@ func (v *validator) visit(filepath string, dest string, lineNumbers string) {
 	v.futureMu.Lock()
 	defer v.futureMu.Unlock()
 	k := futureKey{filepath: filepath, dest: dest, lineNumbers: lineNumbers}
-	if _, ok := v.destFutures[k]; ok {
-		v.destFutures[k].cases++
+	// If key present, delete and increment cases.
+	if prevResult, loaded := v.destFutures.LoadAndDelete(k); loaded {
+		newResult := prevResult.(*futureResult)
+		newResult.cases++
+		v.destFutures.Store(k, newResult)
 		return
 	}
-	v.destFutures[k] = &futureResult{cases: 1, resultFn: func() error { return nil }}
+
+	// Key not present, no store.
+	v.destFutures.Store(k, &futureResult{cases: 1, resultFn: func() error { return nil }})
 	matches := remoteLinkPrefixRe.FindAllStringIndex(dest, 1)
 	if matches == nil {
 		// Relative or absolute path. Check if exists.
@@ -291,7 +307,10 @@ func (v *validator) visit(filepath string, dest string, lineNumbers string) {
 
 		// Local link. Check if exists.
 		if err := v.localLinks.Lookup(newDest); err != nil {
-			v.destFutures[k].resultFn = func() error { return errors.Wrapf(err, "link %v, normalized to", dest) }
+			prevResult, _ := v.destFutures.LoadAndDelete(k)
+			newResult := prevResult.(*futureResult)
+			newResult.resultFn = func() error { return errors.Wrapf(err, "link %v, normalized to", dest) }
+			v.destFutures.Store(k, newResult)
 		}
 		return
 	}
diff --git a/pkg/mdformatter/linktransformer/validator.go b/pkg/mdformatter/linktransformer/validator.go
index 1000813..bc75120 100644
--- a/pkg/mdformatter/linktransformer/validator.go
+++ b/pkg/mdformatter/linktransformer/validator.go
@@ -34,7 +34,11 @@ func (v GitHubValidator) IsValid(k futureKey, r *validator) (bool, error) {
 // RoundTripValidator.IsValid returns true if url is checked by colly.
 func (v RoundTripValidator) IsValid(k futureKey, r *validator) (bool, error) {
 	// Result will be in future.
-	r.destFutures[k].resultFn = func() error { return r.remoteLinks[k.dest] }
+	prevResult, _ := r.destFutures.LoadAndDelete(k)
+	newResult := prevResult.(*futureResult)
+	newResult.resultFn = func() error { return r.remoteLinks[k.dest] }
+	r.destFutures.Store(k, newResult)
+
 	r.rMu.RLock()
 	if _, ok := r.remoteLinks[k.dest]; ok {
 		r.rMu.RUnlock()
diff --git a/pkg/mdformatter/mdformatter.go b/pkg/mdformatter/mdformatter.go
index 71793f3..50dafd8 100644
--- a/pkg/mdformatter/mdformatter.go
+++ b/pkg/mdformatter/mdformatter.go
@@ -10,6 +10,7 @@ import (
 	"io/ioutil"
 	"os"
 	"sort"
+	"sync"
 	"time"
 
 	"github.com/Kunde21/markdownfmt/v2/markdown"
@@ -217,7 +218,7 @@ func newSpinner(suffix string) (*yacspin.Spinner, error) {
 
 // Format formats given markdown files in-place. IsFormatted `With...` function to see what modifiers you can add.
 func Format(ctx context.Context, logger log.Logger, files []string, opts ...Option) error {
-	spin, err := newSpinner(" Formatting: ")
+	spin, err := newSpinner(" Formatting... ")
 	if err != nil {
 		return err
 	}
@@ -228,7 +229,7 @@ func Format(ctx context.Context, logger log.Logger, files []string, opts ...Opti
 // If diff is empty it means all files are formatted.
 func IsFormatted(ctx context.Context, logger log.Logger, files []string, opts ...Option) (diffs Diffs, err error) {
 	d := Diffs{}
-	spin, err := newSpinner(" Checking: ")
+	spin, err := newSpinner(" Checking... ")
 	if err != nil {
 		return nil, err
 	}
@@ -240,57 +241,73 @@ func IsFormatted(ctx context.Context, logger log.Logger, files []string, opts ..
 
 func format(ctx context.Context, logger log.Logger, files []string, diffs *Diffs, spin *yacspin.Spinner, opts ...Option) error {
 	f := New(ctx, opts...)
-	b := bytes.Buffer{}
-	// TODO(bwplotka): Add concurrency (collector will need to redone).
+	errorChannel := make(chan error)
+	var wg sync.WaitGroup
 
 	errs := merrors.New()
 	if spin != nil {
 		errs.Add(spin.Start())
 	}
+
+	wg.Add(len(files))
+
+	go func() {
+		wg.Wait()
+		close(errorChannel)
+	}()
+
 	for _, fn := range files {
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		default:
-		}
-		if spin != nil {
-			spin.Message(fn + "...")
-		}
-		errs.Add(func() error {
+		go func(fn string) {
+			defer wg.Done()
+			b := bytes.Buffer{}
+
 			file, err := os.OpenFile(fn, os.O_RDWR, 0)
 			if err != nil {
-				return errors.Wrapf(err, "open %v", fn)
+				errorChannel <- errors.Wrapf(err, "open %v", fn)
+				return
 			}
 			defer logerrcapture.ExhaustClose(logger, file, "close file %v", fn)
 
 			b.Reset()
 			if err := f.Format(file, &b); err != nil {
-				return err
+				errorChannel <- err
+				return
 			}
 
 			if diffs != nil {
 				if _, err := file.Seek(0, 0); err != nil {
-					return err
+					errorChannel <- err
+					return
 				}
 
 				in, err := ioutil.ReadAll(file)
 				if err != nil {
-					return errors.Wrapf(err, "read all %v", fn)
+					errorChannel <- errors.Wrapf(err, "read all %v", fn)
+					return
 				}
 
 				if !bytes.Equal(in, b.Bytes()) {
 					*diffs = append(*diffs, gitdiff.CompareBytes(in, fn, b.Bytes(), fn+" (formatted)"))
 				}
-				return nil
+				return
 			}
 
 			n, err := file.WriteAt(b.Bytes(), 0)
 			if err != nil {
-				return errors.Wrapf(err, "write %v", fn)
+				errorChannel <- errors.Wrapf(err, "write %v", fn)
+				return
+			}
+			if err := file.Truncate(int64(n)); err != nil {
+				errorChannel <- err
+				return
 			}
-			return file.Truncate(int64(n))
-		}())
+		}(fn)
 	}
+
+	for err := range errorChannel {
+		errs.Add(err)
+	}
+
 	if spin != nil {
 		errs.Add(spin.Stop())
 	}