diff --git a/src/components/AutoComplete/AutoComplete.tsx b/src/components/AutoComplete/AutoComplete.tsx
index 350c332..ba9c6a2 100644
--- a/src/components/AutoComplete/AutoComplete.tsx
+++ b/src/components/AutoComplete/AutoComplete.tsx
@@ -26,7 +26,7 @@ export interface Props {
   onBlur?: (event: KeyboardEvent<HTMLInputElement>) => void;
 }
 
-const renderInputComponent = inputProps => {
+const renderInputComponent = (inputProps): JSX.Element => {
   const { ref, startAdornment, disableUnderline, onKeyDown, ...others } = inputProps;
   return (
     <InputField
@@ -46,7 +46,7 @@ const renderInputComponent = inputProps => {
 
 const getSuggestionValue = (suggestion): string => suggestion.name;
 
-const renderSuggestion = (suggestion, { query, isHighlighted }) => {
+const renderSuggestion = (suggestion, { query, isHighlighted }): JSX.Element => {
   const matches = match(suggestion.name, query);
   const parts = parse(suggestion.name, matches);
   return (
@@ -68,7 +68,7 @@ const renderSuggestion = (suggestion, { query, isHighlighted }) => {
   );
 };
 
-const renderMessage = message => {
+const renderMessage = (message): JSX.Element => {
   return (
     <MenuItem component="div" selected={false}>
       <div>{message}</div>
@@ -98,7 +98,7 @@ const AutoComplete = ({
   suggestionsLoading = false,
   suggestionsLoaded = false,
   suggestionsError = false,
-}: Props) => {
+}: Props): JSX.Element => {
   const autosuggestProps = {
     renderInputComponent,
     suggestions,
@@ -119,7 +119,7 @@ const AutoComplete = ({
   };
 
   // this format avoid arrow function eslint rule
-  function renderSuggestionsContainer({ containerProps, children, query }) {
+  function renderSuggestionsContainer({ containerProps, children, query }): JSX.Element {
     return (
       <SuggestionContainer {...containerProps} square={true}>
         {suggestionsLoaded && children === null && query && renderMessage(SUGGESTIONS_RESPONSE.NO_RESULT)}
diff --git a/src/components/Developers/Developers.tsx b/src/components/Developers/Developers.tsx
index 7913d7c..9ca8f6e 100644
--- a/src/components/Developers/Developers.tsx
+++ b/src/components/Developers/Developers.tsx
@@ -17,7 +17,7 @@ class Developers extends Component<Props, any> {
     visibleDevs: 6,
   };
 
-  public render() {
+  public render(): JSX.Element {
     return (
       <DetailContextConsumer>
         {({ packageMeta }: any) => {
@@ -54,7 +54,7 @@ class Developers extends Component<Props, any> {
     );
   };
 
-  private renderLinkForMail(email, avatarComponent, packageName, version) {
+  private renderLinkForMail(email, avatarComponent, packageName, version): JSX.Element {
     if (!email || isEmail(email) === false) {
       return avatarComponent;
     }
diff --git a/src/components/Dist/Dist.tsx b/src/components/Dist/Dist.tsx
index 381fff0..bb30498 100644
--- a/src/components/Dist/Dist.tsx
+++ b/src/components/Dist/Dist.tsx
@@ -7,7 +7,7 @@ import { Heading, DistListItem, DistChips } from './styles';
 import fileSizeSI from '../../utils/file-size';
 
 class Dist extends Component<any, any> {
-  public render() {
+  public render(): JSX.Element {
     return (
       <DetailContextConsumer>
         {(context: any) => {
@@ -17,7 +17,7 @@ class Dist extends Component<any, any> {
     );
   }
 
-  private renderChips(dist: any, license: string) {
+  private renderChips(dist: any, license: string): JSX.Element | never[] {
     const distDict = {
       'file-count': dist.fileCount,
       size: dist.unpackedSize && fileSizeSI(dist.unpackedSize),
diff --git a/src/components/NotFound/NotFound.tsx b/src/components/NotFound/NotFound.tsx
index da91ff0..6350558 100644
--- a/src/components/NotFound/NotFound.tsx
+++ b/src/components/NotFound/NotFound.tsx
@@ -12,15 +12,15 @@ export const NOT_FOUND_TEXT = "Sorry, we couldn't find it...";
 export type NotFoundProps = RouteComponentProps & { width: any; history: any };
 
 const NotFound: React.FC<NotFoundProps> = ({ history, width }) => {
-  const handleGoTo = (to: string) => () => {
+  const handleGoTo = (to: string): (() => void | undefined) => () => {
     history.push(to);
   };
 
-  const handleGoBack = () => () => {
+  const handleGoBack = (): ((e: React.MouseEvent<HTMLElement, MouseEvent>) => void | undefined) => () => {
     history.goBack();
   };
 
-  const renderList = () => (
+  const renderList = (): JSX.Element => (
     <List>
       <ListItem button={true} divider={true} onClick={handleGoTo('/')}>
         {'Home'}
@@ -31,7 +31,7 @@ const NotFound: React.FC<NotFoundProps> = ({ history, width }) => {
     </List>
   );
 
-  const renderSubTitle = () => (
+  const renderSubTitle = (): JSX.Element => (
     <Typography variant="subtitle1">
       <div>{"The page you're looking for doesn't exist."}</div>
       <div>{'Perhaps these links will help find what you are looking for:'}</div>
diff --git a/src/components/Package/Package.test.tsx b/src/components/Package/Package.test.tsx
index 99ee5fe..bc29297 100644
--- a/src/components/Package/Package.test.tsx
+++ b/src/components/Package/Package.test.tsx
@@ -8,7 +8,7 @@ import { WrapperLink, Description, OverviewItem } from './styles';
  * Generates one month back date from current time
  * @return {object} date object
  */
-const dateOneMonthAgo = () => new Date(1544377770747);
+const dateOneMonthAgo = (): Date => new Date(1544377770747);
 
 describe('<Package /> component', () => {
   test.skip('should load the component', () => {
diff --git a/src/components/RegistryInfoContent/RegistryInfoContent.tsx b/src/components/RegistryInfoContent/RegistryInfoContent.tsx
index 7ea2b9a..3444cd3 100644
--- a/src/components/RegistryInfoContent/RegistryInfoContent.tsx
+++ b/src/components/RegistryInfoContent/RegistryInfoContent.tsx
@@ -11,7 +11,7 @@ import { getCLISetRegistry, getCLIChangePassword, getCLISetConfigRegistry } from
 import { NODE_MANAGER } from '../../utils/constants';
 
 /* eslint react/prop-types:0 */
-function TabContainer({ children }) {
+function TabContainer({ children }): JSX.Element {
   return (
     <CommandContainer>
       <Typography component="div" style={{ padding: 0, minHeight: 170 }}>
@@ -26,11 +26,16 @@ class RegistryInfoContent extends Component<Props, State> {
     tabPosition: 0,
   };
 
-  public render() {
+  public render(): JSX.Element {
     return <div>{this.renderTabs()}</div>;
   }
 
-  private renderTabs() {
+  private handleChange = (event: any, tabPosition: number) => {
+    event.preventDefault();
+    this.setState({ tabPosition });
+  };
+
+  private renderTabs(): JSX.Element {
     const { scope, registryUrl } = this.props;
     const { tabPosition } = this.state;
 
@@ -48,7 +53,7 @@ class RegistryInfoContent extends Component<Props, State> {
     );
   }
 
-  private renderNpmTab(scope: string, registryUrl: string) {
+  private renderNpmTab(scope: string, registryUrl: string): JSX.Element {
     return (
       <React.Fragment>
         <CopyToClipBoard text={getCLISetConfigRegistry(`${NODE_MANAGER.npm} set`, scope, registryUrl)} />
@@ -58,7 +63,7 @@ class RegistryInfoContent extends Component<Props, State> {
     );
   }
 
-  private renderPNpmTab(scope: string, registryUrl: string) {
+  private renderPNpmTab(scope: string, registryUrl: string): JSX.Element {
     return (
       <React.Fragment>
         <CopyToClipBoard text={getCLISetConfigRegistry(`${NODE_MANAGER.pnpm} set`, scope, registryUrl)} />
@@ -68,18 +73,13 @@ class RegistryInfoContent extends Component<Props, State> {
     );
   }
 
-  private renderYarnTab(scope: string, registryUrl: string) {
+  private renderYarnTab(scope: string, registryUrl: string): JSX.Element {
     return (
       <React.Fragment>
         <CopyToClipBoard text={getCLISetConfigRegistry(`${NODE_MANAGER.yarn} config set`, scope, registryUrl)} />
       </React.Fragment>
     );
   }
-
-  private handleChange = (event: any, tabPosition: number) => {
-    event.preventDefault();
-    this.setState({ tabPosition });
-  };
 }
 
 export default RegistryInfoContent;
diff --git a/src/index.tsx b/src/index.tsx
index 610762a..7c1c83d 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -8,7 +8,7 @@ import App from './App';
 
 const rootNode = document.getElementById('root');
 
-const renderApp = Component => {
+const renderApp = (Component): void => {
   ReactDOM.render(
     <AppContainer>
       <Component />
diff --git a/src/utils/asyncComponent.tsx b/src/utils/asyncComponent.tsx
index b687f6b..9789aa0 100644
--- a/src/utils/asyncComponent.tsx
+++ b/src/utils/asyncComponent.tsx
@@ -1,11 +1,11 @@
-import React from 'react';
+import React, { ComponentClass } from 'react';
 
-export function asyncComponent(getComponent) {
+export function asyncComponent(getComponent): ComponentClass {
   return class AsyncComponent extends React.Component {
     public static Component = null;
     public state = { Component: AsyncComponent.Component };
 
-    public componentDidMount() {
+    public componentDidMount(): void {
       const { Component } = this.state;
       if (!Component) {
         getComponent()
@@ -20,7 +20,7 @@ export function asyncComponent(getComponent) {
       }
     }
 
-    public render() {
+    public render(): JSX.Element | null {
       const { Component } = this.state;
       if (Component) {
         // eslint-disable-next-line verdaccio/jsx-spread
diff --git a/src/utils/file-size.ts b/src/utils/file-size.ts
index 28f20ea..8f547ce 100644
--- a/src/utils/file-size.ts
+++ b/src/utils/file-size.ts
@@ -1,4 +1,4 @@
 /* @ts-ignore */
-export default function fileSizeSI(a?: any, b?: any, c?: any, d?: any, e?: any) {
+export default function fileSizeSI(a?: any, b?: any, c?: any, d?: any, e?: any): string {
   return ((b = Math), (c = b.log), (d = 1e3), (e = (c(a) / c(d)) | 0), a / b.pow(d, e)).toFixed(2) + ' ' + (e ? 'kMGTPEZY'[--e] + 'B' : 'Bytes');
 }